I'm not sure why people get so surprised by these things. Nintendo is known to go after any and everything that violates their trademark in any kind of way. On top of that they claim to be protecting their Virtual Store sales when they go about it, although I call crap on that. Part of this is created by their insistence that each console requires a new virtual console store purchase of the game rather than tying it to the account.

The fact the creator of this had the roms built in was a major red flag, that's a big nono, and in some countries like the US it's a bigger deal because emulators aren't considered legal unless you own the actual console already and you've made it yourself. At least that's my interpretation.

Under United States law, obtaining a dumped copy of the original machine's BIOS is legal under the ruling Lewis Galoob Toys, Inc. v. Nintendo of America, Inc., 964 F.2d 965 (9th Cir. 1992) as fair use as long as the user obtained a legally purchased copy of the machine. However, several emulators for platforms such as Game Boy Advance are capable of running without a BIOS file, using high-level emulation to simulate BIOS subroutines at a slight cost in emulation accuracy.