iGBA: GBA & GBC Retro Emulator stands as a remarkable, lightweight retro emulator tailored to transport you back to the golden era of gaming with the legendary Game Boy family. This emulator is a virtual gem that allows you to relive your cherished childhood moments with classic Game Boy, Game Boy ...
As long as it doesn’t include a bios file, and is completely free (including no in app purchases), I doubt it. Emulators like igba are all over the Google play store, Nintendo only shows its fangs when they try to make money or contain proprietary code.
An emulator, even a paid one, would be totally legal in the US as long as:
It does not use any patented technologies. I'm not sure if Nintendo has any patents in the emulation space, but regardless the GBA is so simple that it wouldn't require patented techniques to emulate.
It does not contain any proprietary (copyrighted) code. On more modern consoles, this would include the BIOS or Firmware files. Does the GBA even need something like that?
Number 1 is a non-issue for a GBA emulator. Number 2 is more tricky, but it's always possible to reverse engineer and reimplement the firmware. That's protected by the Compaq v. IBM case.
The recent drama with the Switch emulator is that they violated the second principle.
Which is probably not copyrightable. A key is just a number, and copyright only applies to creative works. In a court, Nintendo would have to argue that copyright does apply because the key was created via some artistic or creative process by a human. It likely is just the output of a random number generator. Also, we’ve already been through this when people figure out how to decrypt DVDs.
But this app has no ROMs and the search page only takes you to a public domain homebrew ROM page. You can add and run your own ROMs but they don’t even mention it for fear of crossing Apple or Nintendo.