The iOS licensing means that no iOS developer can make an emulator which can load "ROMs" and sell that emulator on iTunes which means any Amiga Emulator would have to be sold WITH licensed games.
This may be the only way to actually sell it and make real money on it anyway, not because Apple say so, but because nobody will know what "ROM"s are, or ADF's, they don't care, they just want to play a collection of games. Like the "Atari greatest hits" above. However, the Atari app *does* sell extra games packs, $0.99 per four-pack (where you get both console and arcade games), or $15 for them all apparently.