Beware of PATCHED Grand Theft Auto! Here's how to tell if the store copy is what you want!
It appears Grand Theft Auto's hole that allows homebrew to run has been patched in the latest copies shipping from Rockstar Games... so, before you buy a copy to run homebrew, MAKE SURE YOU HAVE A VERSION THAT CAN RUN HOMEBREW! Gameplay has *not* been improved by the patch.
So here's how to tell by looking at the spine of the game case...
For the U.S./North American version of the game:
ULUS 10041 means it is *not* patched (confirmed by Jamie at PSPUpdates). We're not sure what the patched ones look like yet.
For the E.U./United Kingdom version of the game:
ULES00151# means it's not patched. However, if it has ULES00151#2 (note the added "2"), then it *is* patched.
For now, your best bet for finding an unpatched copy (and there are probably many still out there brand new) is to buy a used copy at a GameStop or an E.B. Games.
Thanks to PSPUpdates for updating us on this as well.