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.

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.

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.

With over 47,000 GitHub stars, Cal.diy is the fully open-source community fork of Cal.com that strips away every proprietary license gate and enterprise paywall to deliver a pure MIT-licensed scheduling platform you completely own. The booking engine supports individual event types including recurring events, seated events with capacity limits, and paid bookings through Stripe and PayPal, all backed by customizable availability schedules with date overrides, buffer times, minimum notice periods, and travel schedule support. Calendar synchronization is bidirectional across nine providers — Google Calendar, Outlook and Office 365, Apple Calendar, CalDAV, Lark, Feishu, Zoho, Exchange, and ICS feeds — so every booking automatically appears on your existing calendar while blocking conflicting slots. Video conferencing links generate automatically for Zoom, Google Meet, Microsoft Teams, Webex, Jitsi, Daily.co, Whereby, and Huddle01, eliminating manual link management. The automation layer connects through webhooks, Zapier, n8n, Make, and Pipedream to CRM platforms like HubSpot, Salesforce, and Close, messaging services including Discord, Telegram, and WhatsApp, and analytics tools such as Google Analytics 4, PostHog, and Fathom. The entire application is built on the T3 stack — Next.js for server-rendered pages, tRPC for end-to-end type-safe APIs, Prisma for PostgreSQL database access, and Tailwind CSS for the responsive interface. Unlike Cal.com's open-core model, Cal.diy requires no license key and includes no gated features. 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.

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.

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.

Work, personal, business, and school calendars at different providers double-book because no one system sees your real availability - Keeper solves that multi-calendar collision problem. Its pull-compare-push sync engine aggregates events from Google Calendar, Outlook/Office 365, iCloud, FastMail, any CalDAV server, or read-only iCal/ICS feeds, and pushes blocking events to one or many destination calendars so time slots align everywhere. The design is deliberately content-agnostic - it syncs timeslots, not titles or descriptions, so a personal appointment shows as busy time on your work calendar without leaking details. Sync logic is clean: events Keeper creates carry a traceable UID suffix, deletions propagate, and orphaned entries are purged automatically. A token-authenticated aggregated iCal feed combines selected calendars into one subscribable URL for Apple Calendar or Thunderbird. An optional MCP server gives AI agents read-only calendar access over OAuth 2.1 - list calendars and query events by date range, with no write capability. Built with Next.js and Bun under AGPL-3.0, the standalone Docker image bundles web, API, cron, worker, Redis, and PostgreSQL in one container, and self-hosting unlocks every Pro feature - unlimited calendars and one-minute sync intervals - for free.

Calendars, to-do lists, journal entries, and contacts, synced over the open CalDAV and CardDAV standards nearly every client already speaks: Radicale is a small pure-Python server that works with Thunderbird, DAVx5 on Android, Apple Calendar and Contacts, GNOME, and many more. Its defining design choice is radical simplicity: there is no database. Events live as plain .ics files and contacts as .vcf files in an ordinary folder structure, which makes backup a copy command, migration a move, and disaster recovery a matter of reading text files. The server works out of the box with no complicated setup, then grows as needed: flexible authentication (htpasswd files among other methods), per-collection authorization rules, TLS-secured connections, and a plugin system for extending storage, auth, and rights handling. Built-in limits on parallel connections, file sizes, and failed authentication attempts harden it for network exposure behind a reverse proxy. A bundled web interface handles creating and managing calendars and address books - useful since many clients cannot create collections themselves. Maintained since 2011 with 140+ contributors, GPLv3-licensed, and light enough to run on the smallest VPS or a Raspberry Pi.

Worklenz delivers an all-in-one project management platform purpose-built for teams that bill clients for their time and expertise. The task management system supports list, Kanban board, and timeline Gantt views with priorities, due dates, assignees, labels, and subtasks. Built-in time tracking offers both start-stop timers and manual entry, logging billable hours directly against tasks and automatically aggregating time data into project-level cost reports. The resource management module provides a visual team utilization dashboard showing capacity allocation across all active projects, helping managers avoid overallocation and balance workloads. Client portals give external stakeholders direct visibility into project progress, task status, and deliverables without requiring internal account access. Financial insights track budgets versus actuals, showing project profitability, cost breakdowns, and burn rate in real time. The analytics engine generates reports on project health, team workload distribution, task completion trends, and time allocation patterns. Project templates enable one-click setup of common agency workflows with pre-configured task structures, milestones, and assignments. The React frontend uses Ant Design components with TypeScript, while the Express.js backend connects to PostgreSQL for data and Redis for caching. Docker Compose deployment includes Nginx reverse proxy with SSL/TLS support, automated database backups, health checks on all services, network isolation, and MinIO for object storage. On RepoCloud, deploy Worklenz on a dedicated VPS with root SSH access, persistent PostgreSQL storage for your project data, and complete control over client portal access and team configurations, all under the AGPL-3.0 license.

Shelf answers the three questions every equipment manager dreads — who has it, where is it, and when is it coming back — using QR-code-first tracking where every asset gets a unique scannable label, every handover is logged with timestamps and e-signed custody agreements, and every scan captures GPS coordinates displayed on a map. Built on React Router 7 with React 19, TypeScript 5, Prisma 6 ORM, and Tailwind CSS 3 with Radix UI components, the platform generates QR codes and barcodes (Code128, Code39, Datamatrix) printable on DYMO, Brother, and Zebra label printers. The custody system records every handover with user details and generates PDF custody agreements with e-signatures for high-value items, while a complete audit trail tracks responsibility from check-out to return. The visual booking calendar prevents double-bookings automatically, supports partial check-outs and returns with segmented lifecycle bars, and handles quantity-tracked consumables alongside individually serialized equipment. Asset Models enable bulk creation of identical items with shared defaults while maintaining individual QR codes and custody histories. Location tracking displays last-scanned GPS coordinates on MapTiler maps. Supabase Auth provides email and SSO authentication, pg-boss handles background job queuing, and Nodemailer delivers SMTP email. The Shelf Companion app on iOS and Android enables field scanning and bookings. Export Asset Inventory, Asset Distribution, and Custody Snapshot reports for compliance. Deploy via Docker with PostgreSQL and Supabase. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL v3.0 licensed.