Calendly is published by Calendly. This page compares only projects with an explicit relationship to it; shared categories alone never create an alternative claim.
Recommended order uses OpenAlternative organic alternatives v4 (version 4). Relationship confidence, category fit, logarithmic popularity, as-of maintenance and freshness, bounded anomaly quarantine, and known-data penalties. Payment is fixed at zero.
A hard constraint removes a Project only when its stored fact is known and conflicts. Unknown facts remain visible, are called out below, and never become a negative claim.
Scheduling infrastructure you can host and extend
Cal.com covers the booking link case well, but its real distinction is that scheduling is exposed as infrastructure. Availability, event types, and bookings all have APIs, and the booking page can be embedded rather than linked.