Harmonix, who makes the Rock Band guitar controller, created a compatibility patch a couple weeks ago that would allow you to use 3rd party controllers, including Guitar Hero’s guitar, on the PS3 version of their game. Unfortunately, Activision “objected” to the patch and it’s been on ice for two weeks. I’m not sure what they’re getting out of blocking more sales for their game, since if someone wanted to use their guitar, they’d probably have to buy Guitar Hero 3 with it. Seems a kind of shortsighted move, but maybe it’s just all part of their master plan. I kind of doubt it, though.
Harmonix: Activision Blocks Rock Band Guitar Compatibility Patch [Shack News]