Our verdict: the leading open-source Calendly alternative — the self-hostable community edition (Cal.diy) is genuinely MIT-licensed and lets you keep your data on your own servers, but the Cal.com-branded cloud and enterprise product is proprietary, so the flagship most people actually use is open-core rather than fully open source.
Cal.com is scheduling and booking infrastructure — an open-source Calendly alternative for arranging meetings and appointments. It offers configurable event types (durations, locations, buffers, booking limits), availability schedules with two-way calendar sync, conflict detection and automatic time-zone handling, team scheduling (round-robin, collective and managed events), routing forms, automated email/SMS workflows, 100+ app integrations, embeddable booking pages, payments and a public API. It runs as a hosted cloud service or self-hosted via Docker/Node.js, with iOS and Android apps, and is developed by Cal.com, Inc. (United States).
Being honest about scope: the open-source, self-hostable edition — now branded Cal.diy — is published under the permissive MIT license, but the Cal.com-branded cloud and enterprise product is proprietary, an open-core model. In 2026 Cal.com moved its production/cloud codebase into a private repository and relaunched the former public repo (calcom/cal.com, which now redirects to calcom/cal.diy) as MIT-licensed Cal.diy with commercial features (Teams, Organizations, Workflows, Routing, Insights, SSO/SAML) removed; the core was formerly AGPL-3.0-only with a separate commercial Enterprise License for its /ee folder. So the community self-host edition is genuinely open source, while the flagship cloud service most people use is closed source. The hosted product is independently audited (SOC 2 Type II, ISO 27001) and states HIPAA, GDPR and CCPA compliance.
