So I’m talking about playing previously Windows-only games on Linux, e.g. via proton.
I don’t know about the libraries etc that are used - is it possible for Microsoft to use some legal voodoo, for example, to suddenly end it all, and make the use of their libraries illegal (if they belong to Microsoft in the first place)?
Or could there be other ways of interference?
The Wine and Proton devs claim that all of the code has been reverse engineered and written from scratch to simply be compatible with the Windows APIs. Unless that claim is false, or Microsoft has a patent over any systems they are recreating (which is unlikely), there’s nothing Microsoft can do legally. If they did have a patent, getting around it probably wouldn’t be too hard.
A similar case was google reimplementing Sun/Oracle Java APIs. Which has been deemed legal after all.