The minute Nintendo finds out about something, they act aggressively. They fiercely defend their IP.
Compare that to Sega, which loves and almost endorses fan content. Look at the Sonic fandom for instance. They have their own original content, games, music, etc.
Nintendo is strange about it, though. They usually only C&D projects bring their IP to other platforms (discounting emulation for a bit since emulation doesn’t directly infringe). They have allowed numerous ROM hacks to exist completely unimpeded. If Mario Royale had been a combination ROM hack and LUA script/custom emulator, it’d probably still be around. I’m honestly surprised I haven’t heard much about them going after the SM64 ports.
What about the Ocarina of Time rom hack, "Missing Link" [1,2]? That added entirely new worlds and dungeons, but was a rom hack. You could supposedly play it on real Nintendo 64 Disk Drive hardware.
It probably helps that, like with several authorized source ports, a separately-acquired copy of the original game assets are required. I’d imagine some of the enhanced ports (that provide upgraded models and textures) would be more legally shaky, and there must be some other good reason why they wouldn’t go after them.
I find it amusing to imagine Nintendo trying to shut down this game. Like I get that legally they have the right to protect their IP, but realistically, what are they worried about? That this game is a threat to sales of their actual game? Or that people would think this is a legitimate Mario game and get a bad impression of Mario and never buy any of their other games? Both scenarios seem hilarious.
Let them come. Asshole companies shouldn't discourage people from building cool things. Until the C&D arrives, the author ought to express themselves in defiance of Nintendo.
