Open source ontology projects
Every project in the registry tagged ontology, ranked by real GitHub adoption.
World's first open-source enterprise world model.
Plan, apply and roll back changes to a production ontology, with a blast radius report and a proof an auditor can re-check.
Connect your company's data, let an agent draft an ontology over it, and load it into HelixDB as one graph you can explore and ask questions of. Hosted at found
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Frequently asked questions
How many open source ontology projects are there?
This registry tracks 3 projects tagged ontology, with 12,086 GitHub stars between them. The most-adopted is utopia at 8,579 stars.
Are these ontology projects free to use?
Yes — 3 of the 3 carry an explicit open-source licence across 2 distinct licences, so there is no licence fee. Where a project also sells a hosted or enterprise version, the self-hosted path remains free.
Which ontology project should I choose?
The list above is ranked by GitHub stars, but stars measure attention rather than fit. Check three things on each card: the licence (permissive versus copyleft), the language it is written in, and the last-push date — a high-star project that has not been pushed in a year is a liability.
Are these ontology projects still maintained?
3 of the 3 were pushed in the last 90 days, and every card shows its exact last-push date so you can see the rest. Sort your shortlist by that date before committing to a migration.