What "free" means here, precisely

Writing is CC BY 4.0. Datasets are CC0 — public domain, no attribution required, because they are synthetic and there is nothing to attribute. Code is MIT.

No account, no email gate, no "free tier". Nothing is held back for a paid version because there is no paid version.

Take it into your company's onboarding. Translate it. Fork it and delete the parts you disagree with. Teach a paid course from it if you want — CC BY allows that, and we mean it rather than tolerating it.

What free does not mean: unmaintained, or unaccountable. The course has errors and gets corrected in public, in the page, with a note about what changed. Nobody paid for it, which removes the commercial incentive to defend a wrong page rather than fix it.

It also does not mean the material is worth less. The reason it is free is that the marginal cost of a static page is zero and the audience is people who mostly cannot expense a course — not that this is the discount version of something better.

The one thing we ask is the one thing the licence requires: say where it came from.