As far as I could tell from the mess of posts on GBATemp, the "hack" is legit, if you want to call it a hack. They basically just modified the text that displays when an error message is encountered, and then triggered an error to bring up the text. It sounds exactly like when I hacked my old Motorola flip phone to display the Linux penguin on the outside screen instead of the carrier's logo: fun and cool, but entirely useless in terms of hacking the device itself.