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.

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.

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.

Conference rooms, equipment, boats, and even people can be reserved through LibreBooking, a self-hosted scheduler that keeps double bookings off the calendar. Schedules define bookable time slots with custom layouts and seasonal availability, while each resource carries its own minimum and maximum duration, buffer time, lead time, capacity, and optional approval step. Check-in and check-out can release unclaimed slots automatically, and blackout times close resources for maintenance. Quotas stack limits by hours or reservation count, credits meter peak and off-peak usage, and users can buy credits through Stripe or PayPal. Accessories such as projectors or chairs ride along with a booking under their own quantity limits. Groups carry application, group, resource, and schedule administrator roles, and custom attributes extend reservations, resources, and users with text, dropdown, date, or checkbox fields. Reports can be charted, exported to CSV, printed, or emailed, and public resources publish RSS and iCalendar feeds for Outlook and Thunderbird plus an embeddable calendar snippet. A tablet view beside a door shows live availability for on-the-spot booking, a monitor view fills lobby screens, and a Slack command starts a reservation. Sign-in options include LDAP, Active Directory, OAuth2, and SAML, and the REST JSON API automates bookings. Users can join waitlists, request reminder emails, and accept terms of service before booking, while six color themes restyle the interface. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 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.

Used daily by millions of educators and learners in over 65 languages and embedded as the default virtual classroom in Moodle Cloud, Canvas, Sakai, D2L, Jenzabar, and Schoology — together comprising more than 75% of the worldwide learning management system market — BigBlueButton has been the leading open-source web conferencing platform for education since its creation at Carleton University in 2007. The platform delivers WebRTC-based real-time audio, video, and screen sharing with a tldraw v2-powered multi-user whiteboard featuring infinite canvas support, allowing multiple participants to annotate slides and draw simultaneously. Breakout rooms support up to eight concurrent groups with collaborative whiteboards enabled by default, and polling with customizable response types lets instructors assess understanding in real time. The built-in Learning Analytics Dashboard answers three questions at a glance: who is attending, who is participating, and who is learning based on poll responses, providing actionable engagement metrics without requiring webcam surveillance. Session recording captures audio, video, slides, chat, and whiteboard annotations for asynchronous playback on any device. The plugin architecture introduced in version 3.0 enables custom extensions, while IMS LTI 1.0 compliance allows integration with Blackboard, Desire2Learn, Pearson Learning Studio, and any conformant platform without custom code. The REST API enables programmatic session management, user authentication, and recording access for custom frontends like the included Greenlight application. Version 4.0 introduces LiveKit-based media and a redesigned interface. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. LGPL-3.0 licensed.

For online classes, telehealth visits, and support calls, OpenVidu Meet is a video meeting app that anyone with a link can join from a browser, with no account or download. A room needs only a name, and an optional wizard adds limits on participants (up to 30) and meeting length (up to a day), plus microphone and camera defaults. A shared Moderator or Speaker link admits anonymous guests, a personal link identifies each invited guest, and registered users sign in with their accounts. Developers can embed a room with an iframe or web component, and webhooks report meeting events to as many endpoints as needed. A smart mosaic favors recent speakers and counts the participants it hides, and a status rail shows the recording light, an encryption badge, and the time left. Moderators mute one participant's microphone, camera, or screen share, switch them off for everyone, remove people, and promote others. Virtual backgrounds blur the room or swap in an image, before joining or mid-call. Recordings start by hand or when the first participant, the second participant, or a moderator joins, in grid, speaker, or single-speaker layout. Permitted members can play, download, delete, or share saved recordings by link. End-to-end encryption protects audio, video, chat, and names behind a shared passphrase, though encrypted rooms cannot be recorded. 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.

Backed by nearly 30,000 GitHub stars and powering millions of meetings through meet.jit.si, Jitsi Meet is the open-source video conferencing platform that runs entirely in the browser with no plugins or downloads required. The WebRTC-based architecture delivers HD audio and video through the Jitsi Videobridge selective forwarding unit, while Prosody handles XMPP signaling and Jicofo manages conference focus and orechestration. End-to-end encryption uses AES-GCM 128-bit keys exchanged via the Olm protocol, protecting audio, video, and screen sharing through the Insertable Streams API in Chromium-based browsers. Moderators can split participants into breakout rooms with individual password protection, enable lobby waiting rooms for admission control, set meeting passwords, and track speaker statistics with per-participant talk time metrics. Virtual backgrounds leverage TensorFlow.js body segmentation with WebGPU and WebGL acceleration, automatically adapting quality through device tier detection. Server-side recording and YouTube live streaming run through Jibri, while Jigasi provides a SIP gateway for PSTN dial-in and speech-to-text transcription. The platform includes in-meeting chat with private conversations, polls, raise-hand functionality, emoji reactions, and tile and speaker view layouts. Mobile applications for iOS and Android complement the web client, and both web and native SDKs enable embedding video conferences into custom applications. 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.

Seatsurfing brings desk booking, room reservations, and parking management to interactive floor plans across multiple office locations, solving the coordination headache of hybrid work. The Go backend serves two React/TypeScript frontends through a single Docker container on port 8080: a Booking UI built as an installable Progressive Web App for mobile and desktop reservations, and an Admin UI for floor plan configuration, capacity enforcement, and analytics. Interactive floor plans accept uploaded office layouts where administrators visually place bookable spaces with per-space metadata and availability rules. Multi-location support handles organizations with distributed offices across multiple buildings and cities. The buddy system displays which colleagues have bookings on a given day, enabling team coordination without manual communication. Capacity management enforces occupancy limits per area with automatic denial when thresholds are reached. SSO integration supports OIDC and OAuth2 providers including Microsoft Azure AD, Keycloak, and Authentik for enterprise identity federation. Microsoft Teams and Confluence integrations embed booking directly into collaboration tools employees already use daily. The REST API enables automation and custom integrations, while the analytics dashboard tracks utilization rates, peak hours, and booking patterns. Docker Compose deployment requires only a PostgreSQL database with multi-architecture images supporting amd64 and arm64. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.

Organizers running sports leagues, gaming tournaments, and community athletics can deploy Bracket as an open-source competition control hub that coordinates multi-stage events without recurring SaaS subscription fees. Competition directors can configure multi-tier tournament topologies combining single elimination, double elimination, round-robin pools, and dynamic Swiss format brackets within a unified event schedule. An interactive calendar grid enables operators to drag and drop fixtures between designated courts, assign start times, and balance player recovery intervals across multiple playing areas. Public dashboard displays generate real-time match outcomes, court assignments, and standings boards that spectators can monitor on mobile devices or overhead venue monitors with customized team logos. Club administrators can manage multiple regional athletic organizations, register rosters through bulk CSV spreadsheet imports, and coordinate simultaneous divisions spanning amateur and championship flights. Integrated OpenAPI REST endpoints allow external scoring overlays, live stream graphic generators, and automated result bots to query match statuses or submit verified referee scorecards programmatically. 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.