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?
How much appetite does Microsoft have for litigation? The Linux community is nothing if not stubborn, and they won’t take this lying down. You’ll definitely have the Free Software Foundation and the Electronic Frontier Foundation involved and they’ll fight it all the way to the Supreme Court.
I genuinely think that in this respect the answer is quite literally none. I think as bad as Microsoft was in the past—and still is in some respects (e.g. workers’ rights and the whole AoE Mobile debacle)—they seem genuinely committed to doing the right thing as far as open source is concerned. I was merely answering with what is possible, not what I think likely.