Ah, I misunderstood and see what you're referring to now. It looks like the way YouTube auto-truncates URLs caused the link to get mashed into the next line of text on the preview Lemmy fetched. As others mention, that's more of a Lemmy bug than anything.
They're much more likely to spend time on the easy wins than on anything that'll take time and money to fight in court. Since these folks aren't redistributing any of Nintendo's copyrighted content, it's not as simple of a takedown as an emulator that includes private keys.
Github isn't taking Nintendo to court over one of their users projects. They just comply with the takedown request and remove it. The user/dev isn't going to fight Nintendo to bring it back either.
Just in case you are still curious, and I don't see any actual answers here. The download provided is all the code for the game engine and everything else that would be going on in the background of the game. Anything that could be copyrighted by Nintendo (things like character and object models, textures, music, and environments) need to come from a totally legit dump from an official Nintendo cartridge and definitely not any ol' .rom file you can download online