Apple has a long and bizarre history of approving apps one day and then backtracking the next and pulling the apps from the App Store because they shouldn’t have been approved. Generally, Apple doesn't approve any sort of unofficial gaming emulators for purchase on the App Store instead favoring the official sort like the cool Atari app with tons of retro games inside.
We expect the latest mame app will be pulled very shortly, so if you are the retro gamer sort you might want to grab it while the grabbing is good. The app is called iMAME and for now, it is available. The app has a bunch of classic arcade games inside. I will admit that I have never heard of these games so classic might be a stretch.
The games include Circus, Side Track, and Hard Hat. Gottabemobile reports that you can load other game into the emulator, assuming you have the needed geek skills. The games are wrapped in a virtual arcade cabinet, which is quite irritating looking. Apparently, the virtual controls aren’t that great either. That said, it will work with the iCade cabinet if you have one, just like that Atari app.