As I understand it, relicensing is possible when a project has a Contributor Licensing Agreement (CLA) which says that you're signing over your copyright to your contribution to the project's owners. (Who will eventually be bought out by the worst rich person you can think of - Yes, him.)
I peeked in uv's contributing guide and issues and didn't see any CLA. In PyTorch the CLA was mentioned at the top of the contributing guide.
Although, there should have been a community fork of the last FOSS version of Anaconda. That's what happened with Redis, and Redis uses a CLA: https://github.com/redis/redis/blob/unstable/CONTRIBUTING.md...
Don't ever sign a CLA, kids. Hell, only contribute to copyleft projects. We get paid too much to work for free.
Not having a CLA prevents relicensing but open source licenses aren't revokable anyways.
That's not been tested much in the courts. Recent rulings suggest OSS at least has consideration and thus can't be blanket terminated without some justification, but the USC provides that justification (with some onerous requirements -- 2-10 years of notice, has to happen in a certain time window, ...), even for licenses stating irrevocability.