The source code for the OpenGL version wasn't taken down, because it technically doesn't have any Nintendo assets or code (which is why they haven't DMCAed it). It requires a (not included) .Z64
ROM of the US or JP version of the game, and must be compiled (more info on that), but I'm not sure what our stance is.
Talk:Super Mario 64
Based on what you said, I don't see a problem linking it. It doesn't seem any different than linking to a Nintendo 64 emulator, since people who legally own Super Mario 64 should be able to play it.
Man, this port made me want to download it and play it, for the first time. I was always reluctant to get an illegal rom, but this is something that doesn't happen often. It would be amazing if Nintendo could see the potential profit in selling this port. They could get an agreement with the creator of the port and have the game sold officially. Obviously, it's certainly not Nintendo to do such things and I highly doubt they'd wanna embrace the PC platform, but I can always think this would be awesome.