Taken from the front page at Xlr8yourmac.com:
iDVD 3.0.1 runs without Superdrive installed - Some time back I had cloned my iDVD3 folder from a superdrive equipped tower to the PowerBook G4 (w/combo drive), hoping (wishful thinking) that someone would come up with a patch to allow burning to external DVD-R drives in Jaguar (like the short-lived "enabler" for 10.1.5, which didn't work with 10.2.x).