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.

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.