OS 10.3.9
According to the iTunes 7.4 page these are the system requirements:
Macintosh Requirements
* Mac OS X 10.3.9 or later or Mac OS X 10.4.7 or later required for iTunes
* Mac OS X 10.4.10 or later required for iPhone
* 500MHz G3 processor or better
* QuickTime 6.5.2 or later
* 256MB RAM
* Combo/SuperDrive to burn CDs
* Broadband Internet connection (DSL/Cable/LAN) for buying and streaming music
No mention of 10.4+ being needed to sync with iPods.
I'm not going to buy tiger with leopard just around the corner. But I'm still not even sure if my system will run leopard...
Powerbook G4, Mac OS X (10.3.9)