The couple of cheap Logitec and Trust ones I have tried on my iG4 Book never seem to work, it's like they can't get power from the USB ports.
I needed this to get the drivers for the cams I tried and that seemed to work with Skype while they were externally powered (which is not much use with a notebook).
This might help but it's the iBook G4 power issue that would concern me rather than the OS X compatibility.
Mmm.. thinking about it - I have an old 3ccd Panasonic DV cam kicking about - a bit on the big side but would be great quality!
Thanks - I wouldn't have thought about it otherwise.