What is the legal status of recompilation projects like these? Greyer or less grey than emulators?

I'm not aware of legal trouble involving the the Zelda 64 recomp project, which would have a much higher chance of attracting the attention of big N (especially now that a new version of OoT is coming out).

At least in the way that I see it, a recomp is like building your own turntable to play your vinyl records, after stydying their grooves and infering how they would sound (so I guess that it would be less gray than an emulator).

No one can say anything, no game rom is ever bundled in the official releases of these recomps. We always have to provide the roms. Where from, it's another story.