I'm leaning towards "Toozin hasn't seen it yet." Or someone else, for that matter, but who are we kidding. Toozin is everywhere. He's watching us... right now... wait... that kinda disproves my point.
I believe the rule applies only to ROM links and discussions. But since there are a few LEGAL GBA ROMs out there, I think it's perfectly ok to talk about the emulator (I'm planning to make one myself eventually ;) right now I'm working in a NES one :D).
roms of games that belong to nintendo also belong to nintendo, and they are obviously going to use the dmca to prevent piracy as much as they can. the cartridge itself is really insignificant compared to the code thereon. it's illegal to copy a rom, period, since nintendo doesn't release roms and the only legal roms are ones you make yourself (i.e. you own the cart and you copy it to your computer as a backup).
the emulator, though, is a bunch of crackheads' own creation, and they have decided to give it away for free, and no one can say anything about that.