Cal.com

Cal.com is open-source scheduling, the Calendly alternative you can run yourself. Share a link, people pick a slot, it lands on your calendar. The public code recently moved to a repo called cal.diy and relicensed to MIT, and for a solo user it's still free and self-hostable: unlimited bookings, your own branding, your data on your server.

Here's what changed, and it matters. The open build was trimmed back to personal, non-production use. The features teams actually need, shared team scheduling, organizations, SSO, insights, now live in the proprietary hosted product, not the open repo. So the old pitch, "self-host the entire thing," no longer holds once more than one person is involved.

On their cloud, a single user is free, Teams runs $12 per user a month, and Organizations is $28 per user a month. Solo users self-hosting cal.diy pay nothing and lose little. Teams have a real decision now: self-host the trimmed open build and rebuild the team pieces yourself, or pay for the hosted product like you would for Calendly. The "own everything" story is mostly a solo story today.

The catch is the relicensing itself. Cal.com spent years as the AGPL open-core Calendly alternative, and a lot of teams adopted it on that promise. The core is still open and the solo experience is good, but the team features moving behind a proprietary wall is exactly the kind of shift you want to know about before you build a workflow on top of it.