iDOS, a repackaged version of the open source DOSBox emulator, is back on the App Store after getting rid of the ability to load games and other software using iTunes file syncing. While that might make the emulator seem far less useful, users have discovered a simple, no-jailbreak-required hack to load any old DOS software they want to run.

Last year, Apple relaxed several restrictions it had placed on iOS app development, including limitations on running certain interpreted code. This change made it possible to sell hardware emulators like C64 and iDOS via the App Store, "as long as the resulting apps do not download any code," according to Apple.

iDOS originally allowed users to copy arbitrary DOS executables ( .exe files) using the iTunes file syncing capability. The .exe files would be copied to the app's sandboxed file space, which the emulator used as its C: drive. However, since that ability essentially allowed users to download code, it put the app on the wrong side of the iOS developer agreement. Apple subsequently pulled iDOS from the App Store.

Developer FastIntelligence removed the iTunes file syncing ability, instead opting to include six old DOS games along with the app (presumably with the publishers' permission). That got the app back in the App Store, but the developer warned in the release notes that users who rely on iTunes file syncing should "think thrice before updat[ing]."

Not to be thwarted by such restrictions, a user noted a simple hack that allows users to copy over old game files or other .exe files to run on the emulator. A freeware app called iPhone Explorer lets users mount an iPhone to access its filesystem and "use the easy drag-and-drop methods to add or remove files and folders from the iPhone." Using iPhone Explorer, .exe files can be copied to iDOS's "Documents" file area without jailbreaking, essentially replacing iTunes file syncing.

No one outside of Apple knows if the app will be removed once again, but using iPhone Explorer to side-load DOS software isn't under the developer's control. iDOS, as it is sold, doesn't appear to violate any of Apple's App Store rules, so game away while you can.