It took the guys four months to hack it, but The Specialist has been credited with the hack. As far as I know it is something to do with the drives firmware and the hack allows the 360 to run backed-up games.
Also this supposedly works on both DVD drives types. The guys aren't going to release the hack because this would allow modified games to run on Live (as far as I can tell anyway). If you read the thread lookout for comments by TheSpecialist and robinsod.