There are entire categories of apps that aren't allowed by the rules (although you do occasionally find some examples in the store somehow). Emulators that can

There are entire categories of apps that aren't allowed by the rules (although you do occasionally find some examples in the store somehow). Emulators that can run ROM files are a good example. You won't find MAME in the app store except occasionally when someone at AppleHQ makes a mistake. Even then it quickly disappears.