Reverse engineering is legal - reverse engineering a console is entirely legal. Copying the manufacuters IP is illegal, so should be avoided. Dumping the contents of your own cartridges falls under "Fair Use" terms, at least in the US and UK. Downloading images from the internet is obviously illegal, I'd even say it's illegal if you own the physical cartridge, but that might be a grey area. Nintendo have long used scare tactics to restrict emulator development, they threatened to sue the developers of N64 emulator UltraHLE but never followed through with their (empty) threat. I can understand why Nokia have withdrawn the N900 Nintendo emulators, but don't think Nintendo have a leg to stand on. Back on topic: Hasn't this iPhone/N64 emulator been shown to be a hoax? I can't see the videos as youtube is blocked at work but I've read the kid is playing a video of an N64 game (playing on a real N64) on his iPhone and just moving his hands to match the onscreen movement. The Mupen64/Mupen64Plus N64 emulators only support x86 right now - no ARM support.