If the hack does prove to be legitimate, the AppStore could be facing a major issue. Super Monkey Ball for example, sells for $10 USD on the store and is protected with the DRM that Apple has been using for years on its music and videos in the iTunes store.
The original post on Haklabs also provides step-by-step installation instructions for the game and hopes other hackers will help share cracked iPhone apps.
There has been no comment from Sega or Apple as of yet.
Update: It appears the crack is completely legitimate and many games and other applications have already been cracked, including Crash Nitro Kart and Super Monkey Ball. The patching of the checksum should work indefinitely.