Yoga studios, comedy clubs, choirs, and bands use Revel to sell tickets, memberships, and season passes from their own server with no platform fee. Studios and clubs sell monthly or yearly memberships through Stripe and offer series passes that cover a class pack, a course, or a season, with wallet cards that a door scan verifies. Venues design seat maps with sectors, individual seats, and accessible seats, and buyers pick seats on an interactive map while the seats are held at checkout. Bands and DJs sell their own shows with no promoter in between, set pay-what-you-can tiers, open presales to invitation-link holders, and export every buyer's name and email. Communities that vet who comes screen requests with questionnaires reviewed automatically, manually, or both, and keep private guest lists, invitation-only events, and a fuzzy-matched blacklist. Buyers check out a multi-tier cart without an account, using discount codes and fixed-price, free, or pay-at-the-door tiers. Tickets arrive as QR PDFs or Apple Wallet and Google Wallet passes, and door staff check guests in by scanning. Organizers run waitlists with time-limited offers, announcements, reminders, and a Telegram bot for RSVPs and invitations. Revenue and VAT reports export as XLSX or PDF, and VIES checks buyer VAT IDs. The web app speaks English, German, Italian, French, Spanish, and Portuguese. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Hi.Events is an alternative to Eventbrite, Tickettailor, and Dice.fm, eliminating per-ticket platform fees entirely when self-hosted. Event organizers create fully brandable event pages supporting paid, free, donation, and tiered ticket types with recurring and multi-date scheduling, sold-out waitlists that automatically release tickets when spots open, and product add-ons with category organization. Stripe Connect integration processes payments directly to the organizer's bank account with instant payouts, while offline payment methods support cash and invoice scenarios. Promo codes offer fixed or percentage discounts with usage limits, expiry dates, and promo-gated hidden tickets for VIP access. QR code check-in enables fast door scanning with multiple check-in lists, scan logs, and real-time attendance tracking across entry points. Custom checkout questions collect attendee information beyond standard fields, with advanced search, filtering, CSV and XLSX export, full and partial refunds, and bulk attendee messaging. The analytics dashboard tracks daily sales, revenue, tax breakdowns, product performance, and promo code usage with exportable reports, while affiliate tracking assigns custom codes to promoters with tracked sales data. Multi-user roles control organizer permissions, automatic invoicing generates receipts, and the REST API ships with interactive OpenAPI documentation. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Pretix powers thousands of events and millions of ticket sales through a fully brandable ticket shop with interactive seating plans, 30+ payment providers, and a mobile check-in app for venue entry management. With over 2,400 GitHub stars, it delivers what organizations need when they demand full control over attendee data and revenue rather than surrendering margins to Eventbrite or Ticket Tailor. Built with Python and Django on PostgreSQL with Redis and Celery, the ticket shop adapts to your colors, logo, and domain with responsive design. The graphical seating plan editor handles everything from small cinemas to large stadiums, letting buyers choose seats mapped to pricing categories. Payment providers connect through plugins including Stripe, PayPal, Mollie for iDEAL and Bancontact, SEPA direct debit, and bank transfer with automatic CSV import for payment matching. The voucher engine generates bulk discount codes with usage limits, quota reservations, and automated email distribution. Waiting lists automatically offer released tickets to the next registrant with expiration deadlines. A built-in mini-CMS hosts event descriptions, terms of service, and static pages directly in the ticket shop. Customer accounts enable repeat buyers to check out faster across events. The pretixSCAN mobile app performs QR code check-in on Android and iOS with offline capability. Embeddable JavaScript widgets integrate the shop into any website. Plugin architecture extends functionality with output formats, analytics, and Apple Wallet passes. Deploy via Docker with the pretix/standalone image alongside PostgreSQL and Redis. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Alf.io handles the complete conference and event lifecycle from ticket distribution through check-in to financial reporting, built for organizers who refuse to surrender attendee data to third-party ticketing platforms like Eventbrite or Tito. Built on Java 17 with Spring Boot and PostgreSQL with row-level security policies, the project has earned over 1,500 GitHub stars from privacy-conscious event organizers across Europe and beyond. Payment processing supports Stripe for credit cards, Mollie for iDEAL, Bancontact, KBC/CBC, and Przelewy24, plus Revolut, PayPal, bank transfers, on-site collection, and configurable custom offline payment methods with localized instructions. Multi-tier ticket categories enable early bird, VIP, standard, and free registrations with promotional codes, group discounts, and waiting lists that automatically notify next-in-queue when cancellations occur. Customizable registration forms collect attendee data beyond standard fields, while EU VAT management validates tax IDs through the VIES web service and supports Italian e-invoicing with automatic PDF invoice generation attached to confirmation emails. The Alf.io Scan mobile app for iOS and Android performs QR code check-in at venue entrances, and the Alf.io-PI project provides Raspberry Pi-powered offline-capable check-in stations that form encrypted clusters for high-throughput badge printing at large events. Apple Wallet integration delivers digital passes via PassKit. The extensions system integrates with CRMs, accounting platforms, Slack, Telegram, and Mailjet. Multi-language support covers nine languages. Deploy via Docker with PostgreSQL. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPLv3 licensed.

From the call for abstracts to the badge handed over at the registration desk, Indico handles every step of running a conference, plus the weekly meetings and one-off lectures that fill the calendar around it. Events live in a nested tree of categories, and access rules can be set per category, event, session, or single contribution, with custom roles inside each event. Speakers submit abstracts, track reviewers score them against questions the organizers define, judges accept or reject them, and accepted talks become contributions that sit in a drag-and-drop timetable of color-coded sessions. Registration forms are assembled field by field, carry fees, and take payment through PayPal, Stripe, or SIX Payment plugins; attendees get QR-coded tickets, and a badge editor prints name tags for the whole room. A paper reviewing workflow collects full papers. Meeting pages keep minutes and slide decks attached to the talk they belong to. The room booking module adds approvals, recurring reservations, and audiovisual equipment, and the Zoom plugin creates online sessions straight from an event page. Calendar views span a month, week, or day, filter by category, and export to iCal for subscriptions. Scripts pull event data from the HTTP export API as JSON or XML with personal API tokens. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

What Doodle did before ads and paywalls took over: Rallly (three L's) lets you propose a few dates, share a link, and watch an availability grid fill in - no email threads, no forced accounts, no "$6.95/month to remove ads." The availability grid makes the winning slot obvious at a glance, comments on each poll keep the "I can do Tuesday if we start late" discussion attached to the decision instead of buried in chat, and email notifications fire as votes and comments arrive. When consensus lands, finalize the winning option and everyone gets notified. The stack is modern TypeScript - Next.js, tRPC, Prisma over PostgreSQL, Tailwind - with a clean, genuinely mobile-friendly UI, dark mode, and community translations in 10+ languages. Self-hosting means unlimited polls and unlimited participants with meeting data on your server rather than a scheduling SaaS. It pairs naturally with Cal.com: Rallly answers "which time works for everyone?", Cal.com handles "book a slot on my calendar." AGPL-licensed.

Scheduling infrastructure, not just a booking page - Cal.com is the leading open-source scheduling platform. Share a link, attendees pick a slot, and real-time sync against Google Calendar, Outlook, and CalDAV prevents double-booking. Beyond the basics it covers team workflows: round-robin distribution, collective availability across multiple hosts, recurring meetings, and routing forms that ask bookers questions and send them to the right team member - the feature sales and support teams usually pay enterprise prices for. Paid bookings run through Stripe, video calls through the built-in Cal Video (Daily.co) or Zoom and Google Meet, and an app store connects 100+ tools including HubSpot, Zapier, and n8n. The API-first architecture with webhooks and embeds makes it practical to build scheduling into your own product, white-labeled with your domain and branding. Built on Next.js and Prisma over PostgreSQL, translated into 65+ languages, with the self-hostable community codebase maintained under an open-source license.

Service businesses get a booking page without per-booking commissions or monthly SaaS fees from Easy!Appointments, the self-hosted appointment scheduler. Customers pick a service, provider, and open time slot from a clean web form; the system enforces working plans, breaks, and booking rules you define per provider, then confirms by email to both sides. The structure fits real service organizations: multiple providers with individual schedules, multiple service types with their own durations and prices, and admin/secretary roles for front-desk management. Two-way Google Calendar synchronization keeps each provider's external calendar authoritative - book in Easy!Appointments and it appears in Google Calendar, block time in Google and the slot disappears from the booking form. Version 1.6 adds SMS notifications and payment support, and a REST API opens the scheduling data to custom integrations. Built on PHP (CodeIgniter) with MySQL, it installs in a single folder and can share a database with your existing site; a WordPress plugin embeds the booking form directly in pages or posts. The interface ships in dozens of languages with time-zone handling throughout. GPL-3.0 licensed and free for commercial use - a helpdesk, clinic, salon, or consultancy runs its whole booking workflow on its own server.

One binary replaces your booking link and your meeting room: Calnode is a complete scheduler you run yourself, small enough to audit and cheap enough to forget. Create event types with durations, custom questions, and locations, set DST-correct availability with date overrides, and share a booking page where guests pick a slot, reschedule, or cancel without an account. Two-way sync with Google Calendar, Microsoft 365, and CalDAV checks real free and busy time across every connected calendar, then mints Meet or Teams links automatically. Teams route bookings round-robin, collectively, or by priority, while paid event types collect through Stripe before the slot confirms. Choose Calnode Rooms and the meeting itself happens in the browser on your LiveKit server, with host controls, consent-aware recording into your own storage, and an AI notetaker that files a transcript and summary on the booking. Agents get first-class access through the REST API, HMAC-signed webhooks, and a native MCP server, and visitors can even book by describing a time in plain language. Everything runs from one static binary and one SQLite file with streaming Litestream backups. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache-2.0 licensed.

Share a link, and let people book time with you without the email volley that usually decides when a meeting happens. calrs connects to the calendar you already use, whether that is Nextcloud, Fastmail, BlueMind, iCloud, or any other CalDAV server, computes your real free and busy times from synced events and your availability rules, and shows guests only the slots that genuinely work. Create event types for intro calls, support sessions, or coaching, each with its own duration, buffers, minimum notice, booking limits, and confirmation mode, then publish them on your public profile or keep them private behind single-use invite links. Teams get round-robin scheduling that picks the least busy member, collective meetings that require everyone free, and dynamic group links that intersect several calendars on the fly for a one-off call. Guests pick a slot in their own timezone, receive HTML email with calendar invites attached, and can cancel or reschedule themselves from the confirmation email, while you approve pending bookings from the dashboard or straight from your inbox. When a slot looks wrong, the availability troubleshooter draws a timeline showing exactly which event or rule blocked it. Reminders go out before meetings, credentials are encrypted at rest, and the whole interface speaks ten languages with seven themes. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Built on Elixir's fault-tolerant OTP runtime, Tymeslot delivers the complete scheduling toolkit that Calendly charges for and Cal.com relicensed away from open source in 2026. Share one booking link and let clients pick available slots — your calendar stays synchronized and double-bookings disappear automatically through real-time availability checking against Google Calendar, Microsoft Outlook, and any CalDAV server including Nextcloud. Meeting types support configurable durations, buffer times, and availability windows that clients can book without email back-and-forth. Phoenix LiveView powers the real-time UI with WebSocket connections that update instantly as bookings arrive, without client-side JavaScript framework overhead. The platform attaches Zoom video rooms to confirmed bookings through your own Marketplace app credentials, sends confirmation and reminder emails via SMTP, Postmark, SendGrid, Mailgun, or AhaSend, and supports custom booking page themes with embed options for integration into existing websites. Circuit breakers, connection pooling, and graceful degradation maintain availability during provider outages. Authentication supports local accounts, GitHub OAuth, and reCAPTCHA protection on public booking forms. Self-hosting deploys as a single container with PostgreSQL embedded — no separate database container required. Two named volumes persist uploads and database state, while the same image powers the managed cloud at tymeslot.app so self-hosted users get identical features without a crippled community edition. Deploy via Docker, Cloudron with automatic updates, or Railway from a community template. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

One link replaces the scheduling dance: Thunderbird Appointment publishes your availability as a booking page where visitors choose a slot and the meeting lands on your calendar. You connect the calendars you already keep, Google Calendar or any CalDAV server, and the service reads your busy times and writes new bookings back as real events. Weekly schedules define the days and hours on offer, the length of each slot, and how far ahead or how last-minute a booking may be. Each booking page carries its own title, agenda, and location, from a street address to a Zoom link created for the meeting automatically. Visitors see open times in their own timezone, pick one, and leave their name and email; no account is required on their side. Requests can land as confirmed bookings right away or wait for your approval first, and every booking appears in your bookings list with attendee details. Your own calendar view gathers every connected calendar in one place, so personal and work commitments stop colliding. The interface speaks several languages, honors light and dark themes, and lets each user set the week start and 12 or 24 hour clocks. Self-hosters sign in with a password, and larger deployments can plug in an OIDC provider for single sign-on. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MPL-2.0 licensed.

Video meetings on your own domain, branded your way, with no per-host bill: PlugNmeet is a self-hosted web conferencing system that runs full meetings in the browser. The room covers HD video and screen sharing, a collaborative whiteboard that annotates PDFs and office files, a shared notepad, chat, polls, and breakout rooms. Classes use raise hand, waiting rooms, per-user locks, and quiz-mode polls; webinars stream out over RTMP to YouTube or take in an OBS feed. Every meeting can be recorded to MP4, joined by phone through SIP dial-in, and captioned, translated, transcribed, and summarized by an AI agent connected to your own provider. Moderators manage participants and permissions, optional end-to-end encryption keeps even the server out of the media, and plugins drop the same rooms into WordPress, Moodle, Joomla, or any LMS over LTI. Behind it, APIs and PHP or JavaScript SDKs create rooms and mint join tokens from your product. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Passive slide decks put audiences to sleep, which is why Claper turns any presentation into a two-way live session where every attendee can vote in polls, submit questions, and react in real time from their phone. Speakers upload existing PDF or PowerPoint decks directly into the web studio and interleave interactive poll, quiz, form, and web embed slides between their static pages without rebuilding presentations from scratch. Conference organizers and educators share a short join code or QR link so hundreds of participants can enter the attendee room instantly from any mobile browser without installing an app or creating an account. During the talk, the presenter console displays incoming audience questions sorted by upvote popularity, alongside moderation controls to approve, pin, hide, or mark inquiries as answered on the main screen. Live polling supports multiple-choice, rating scale, and open-text prompts that animate into real-time bar charts and percentage breakdowns as votes arrive, while timed quizzes grade participant responses automatically. Integrated real-time speech transcription generates live captions and searchable session transcripts so international and hearing-impaired attendees can follow every spoken word. Universities and corporate training teams connect Claper directly to Moodle or OpenID Connect identity providers via LTI 1.3 to synchronize student rosters, push quiz scores to gradebooks, and export complete CSV engagement reports after every session. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

By turning any browser into an interactive trivia controller and live scoreboard, Razzia gives event hosts, educators, and communities a self-hosted multiplayer quiz platform that replaces Kahoot. Players join in seconds with a six-digit room PIN or scannable QR code on their smartphones, while the host drives the shared screen from a password-protected manager console. Build quizzes directly inside the browser-based editor or import portable JSON files with single-choice, multiple-choice, numeric estimation, and ungraded survey questions. Attach images, audio clips, or video files up to 100 MB to any prompt, group questions into themed round categories, and display explanatory notes when correct answers are revealed. Scoring adapts to your rules: reward fast responses with time-weighted points, apply strict, balanced, or lenient multi-select grading, deduct penalties for wrong guesses, or switch to survey mode to gather live audience polls without a leaderboard. Hosts can lock rooms mid-game, enable automatic nickname generation, hide question prompts on player screens, and configure auto-advance timers between rounds. Drop a custom theme file and logos into the branding folder to white-label colors, fonts, and backgrounds, or connect physical ESP32 hardware buzzers over the documented WebSocket protocol. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

For clubs, associations, and federations, Hitobito replaces the member spreadsheets, sign-up forms, and mailing tools with one web application that mirrors how the organization is actually built. Chapters, regions, committees, and boards sit in a single group tree, and each person holds one or more roles that decide what they can see and change. People tables filter, import, and export to CSV, Excel, vCard, and PDF. Each record carries households, tags, notes, qualifications, and history, and a duplicates view helps clean up double entries. Events and courses accept online registrations, send overflow to a waiting list, and award qualifications that expire or renew by rule. Messages reach mailing lists as bulk e-mail, PDF letters, or SMS, and bounces are collected. The invoicing module issues single invoices and invoice runs, follows each through draft, issued, partially paid, paid, and reminded states, and can import bank payments over EBICS. Administrators edit texts, labels, tags, and course categories without writing code. Other systems sign in through an OAuth 2.0 and OpenID Connect provider and read data through a JSON:API with personal tokens or service accounts. The interface switches between German, English, French, and Italian. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Admidio is membership management software for clubs, associations, and groups, built so that every permission follows from the roles a person holds. Organizers define roles such as board, youth team, or trainers, decide who may email or see each one, and grant module rights like managing events, editing contacts, or uploading photos with simple switches. Contact records use customizable profile fields, record relationships such as parent and child, and can be imported in bulk or exported as vCards. New members register online and administrators review each request. Events carry dates, venues, calendars, and participant lists with sign-up, and the schedule downloads as iCal. Messages go as HTML email to individuals, roles, or groups, and members also find announcements, a categorized forum, document folders with role-based access, and photo albums with e-cards. The inventory manager tracks equipment, who holds it, and its borrowing history. Optional two-factor login protects accounts, a change history can be switched on for every module, and single sign-on lets other applications authenticate against the member database. Twenty-five languages are included, the interface installs as a progressive web app, and sub-organizations can be managed from the same installation. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-2.0 licensed.

Church offices juggle member directories, giving records, event rosters, and volunteer schedules, and ChurchCRM, a free church management system, brings all of it into one browser-based workspace. Administrators keep a record for every person and family, with contact details, roles, notes, custom properties, and a timeline, while visitors submit a self-registration form that staff approve before it reaches the printed directory. Treasurers log donations against family pledge accounts, follow numbered giving envelopes and multi-year pledges, and batch gifts into deposit slips with printable bank forms. Ministry leaders organize teams, committees, Bible studies, and Sunday School rosters, then schedule volunteers into positions with substitutions and reminder email. Events can be one-time or recurring, appear on month, week, day, and list calendars beside birthdays and anniversaries, and collect attendance through kiosk tablets that alert parents by email or SMS. Members sign in to a portal to update their details, confirm their household, and check the church calendar and their volunteer schedule. A family map shows where households live and which ones are close by. Reports produce directories, mailing labels, birthday lists, financial statements, and custom queries, while CSV import, an Export Hub, and one-click database restore handle moving data. Role-based permissions and two-factor sign-in protect sensitive records, and plugins add MailChimp and Vonage SMS. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Keep your newsletter audience on infrastructure you own with LetterSpace, a self-hosted platform for subscriber lists, campaigns, and email analytics. Organize subscribers into lists inside your organization, enrich each address with metadata pairs, and use those values as placeholders inside the mail you send. Campaigns begin as drafts where subject, content, template, target lists, and tracking choices stay editable until you deliberately start the send. A test copy goes to your own inbox first, and a future schedule time holds the campaign until the moment arrives. Reusable HTML templates wrap every campaign in your house style, with the content injected at send time and an unsubscribe link in the footer. Once mail flows, the dashboard follows subscriber growth across six months, recent campaign delivery rates, and open and click performance compared between the last thirty days and the period before. Delivery itself runs through your SMTP settings with per-organization rate limits, retries, and concurrency controls, and provider webhooks can report bounces and confirmations back into message statuses. Signup forms and external tools connect through a REST API guarded by keys, with double opt-in available for new subscribers. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Seven million emails from a single binary peaking at 57 MB of RAM: listmonk is a high-performance newsletter and mailing list manager in Go with PostgreSQL as its only dependency - no Redis, no worker processes, no message broker. The project's own production benchmark sent 7+ million emails with the binary peaking around 57 MB of RAM, and throughput exceeds 100K emails per hour on modest hardware. Campaigns run through a multi-threaded, multi-SMTP queue with round-robin delivery, per-server concurrency, retries, and sliding-window rate limiting across providers like Amazon SES, SendGrid, Mailgun, or your own Postfix relay. Subscribers carry custom JSON attributes and are segmented with raw SQL queries, so any audience Postgres can express, listmonk can target. Templates use Go template syntax with 100+ functions for dynamic per-subscriber content, and the Vue dashboard reports opens, clicks, bounces, and unsubscribes with automated bounce processing. A REST API handles transactional email and programmatic control, a built-in media library hosts campaign assets, and CSV or API import migrates lists from hosted platforms. The economics are the headline: where Mailchimp pricing scales with list size, listmonk plus Amazon SES sends the same volume for hosting cost plus roughly $0.10 per thousand emails - commonly a 95% reduction - and your email list, a core business asset, stays on your own infrastructure. AGPLv3-licensed; bring your own SMTP provider for delivery.