Why Folium and Tessera's code is now public

Both repos went public the same evening: Folium and Tessera, both under PolyForm Noncommercial 1.0.0. Folium was private until this week and MIT before that. Neither is a big change to what you can do with either tool. Both were already free, local-first, no account, nothing leaving your machine. What changed is whether you can read the thing that makes them work.

A page of screenshots claims, a repo shows

I write about these tools on this site, which means I’m asking you to believe Folium really does export a board as one self-contained HTML file, or that Tessera really runs with no server and no account. A screenshot can’t prove that. A repo can. Anyone can clone either one, read the source, and check whether the claims in my field notes match the code that ships. Keeping the repos private was costing me the best argument I had.

Why not MIT

MIT would say the same thing about openness and skip the harder question: what happens if either tool grows a paid edition later. These aren’t community projects looking for contributors; they’re tools I built for myself first, and MIT hands the commercial option to whoever forks the repo first. PolyForm Noncommercial keeps the part I actually want public: anyone can run it, study it, modify it, use it for personal work, education, research, a nonprofit. Sell it, or a product built on it, and that’s a different conversation, with me.

Tessera splits the license because it has two jobs

Tessera is two different things wearing one name. The tool is software: a static page with no build step, PolyForm Noncommercial, same terms as Folium. The format is a promise to a letter that might sit in a drawer for eighty years, and a promise like that can’t have a landlord. So the format — SPEC.md, the spec docs, the README template — is CC0, public domain, no license to outgrow. The letters don’t need the code to survive. They need the format to, and a format nobody owns is the only kind that reliably does.

Both AI Lab pages now carry a View on GitHub button. Folium’s says it plainly: look, learn, and run it yourself, though a commercial edition is a separate matter. That’s the whole policy in one line.