Twenty

Twenty is the open-source CRM that most obviously wants to be used by people who write software. It is licensed under the AGPL, the repository is busy, and the documented way to run it yourself is a Docker Compose file rather than a support ticket. If your objection to this category is that your customer data lives on somebody else's machine, this is the entry that answers it directly.

The pricing inverts the usual shape. Full customisation, custom apps and workflow automation are all on the cheapest paid tier at US$9 per user. What the second tier at US$19 adds is governance rather than capability: row-level permissions, single sign-on, and a custom domain.

On scale headroom it is better equipped than its age suggests, with row-level permissions, single sign-on and an audit log. The tradeoff is the one you would expect of a young project. Integrations are thin — the catalogue does not approach what a decade-old vendor accumulates — self-hosting is only free if your time is, and above the two published tiers sits an enterprise arrangement starting at fifty thousand dollars that is negotiated rather than listed. What you get in exchange is unusual control: run it on hardware you own, read exactly what it does with your records, and take the database with you whenever you want.