Gorhill archives all related repos, so I’m pretty sure active development has enden.

The only “proper” fork I know about is nuTensor:

https://github.com/geekprojects/nuTensor

It has just been forked to provide maintenance though, there probably won’t be any new stuff.

I have to admit that I’m not all that knowledgeable about licensing, so I did a little research and you are totally right. My bad! Legal means would totally be possible then, but that’d require someone actually pressing charges. Since that hasn’t happened yet, I fear it’s pretty unlikely at least in the foreseeable future…

[…] legal ground to force proprietary module vendors to release their source code?

What would make anyone think that? No one has to publish their code. If you really want a FLOSS kernel you’ll have to find open replacements for those modules or make them yourself.