Comment by zerocrates

They haven't been all that aggressive against the decompile/recompile projects, interestingly. They're sometimes/often set up so you need the original to grab assets etc., but that code is copyrighted too and I'd have to imagine a decompile that purposely compiles to an identical binary would be a derivative work.

My best guess is that for them it's not worth the hassle or any possibility of a negative result in court as long as people have to jump through some hoops by providing an original, and for the projects that don't do that, you have very straightforward easy infringement cases without even getting into the decomp stuff. Though really even ROMs seem to be tacitly tolerated to some extent lately. Maybe there's an attitude that keeping people involved with the franchise is worth it, again so long as it doesn't become too easy.