Apparently it changed from 2-clause BSD: https://github.com/bigskysoftware/htmx/commit/e16f1865a494b6...

(The zero clause license drops the requirements for preserving the copyright notice when distributing)

They don't seem to have a CLA so that's interesting...

Why is that interesting?

Without a CLA or equivalent mechanism they would need to get the agreement of every contributor to change licences. Once a project gets large enough the sheer number of people involved usually makes this impossible

(IANAL)

Here's an example where an MIT-licensed project switched to APGL recently without needing to contact contributors[0].

Interestingly, the MIT license explicitly names and allows sublicensing, but the 2-BSD and 0-BSD do not call it out explicitly.

tldrlegal[1] seems to think 0-BSD allows sublicensing, but doesn't mention it on the page for 2-BSD[2]. I'm not sure what to make of that.

[0]: https://github.com/immich-app/immich/discussions/7023#discus... [1]: https://www.tldrlegal.com/license/bsd-0-clause-license [2]: https://www.tldrlegal.com/license/bsd-2-clause-license-freeb...

0-BSD doesn't have any conditions at all. 2-BSD does.

The MIT → AGPL example isn't very illustrative. The requirements under AGPL are a strict superset of the requirements under MIT. Going MIT → 0-BSD is a bit trickier, because distribution under 0-BSD doesn't meet the requirements of MIT.

Twitter Bootstrap had to do that in the early days. Such a pain I wouldn't want for myself.