To me... and I have an old iMac G4 running Mac OS X Leopard (10.5) - it looks like it hasn't got an operating system.
The minimum you will need is Mac OS X Cougar - but the best bet is to install Mac OS X Tiger (10.4) - you can get it if you 'Google' it as an ISO image to install
Once it is installed - you'll need to download an app called 'Leopard Assist' - and this should trick the PowerBook into believing it can run the latest OS X for the Apple G4/G5 computers.
Here are a few links to help you get to know what you've got...
Look for your Apple Computer here amongst this array of G4 MacBooks - you'll find yours among it somewhere
http://www.everymac....werbook-g4.html
Here's the link for the 'Leopard Assist' app...
http://www.macupdate...2/leopardassist
Google for the Mac OS X Tiger (10.4) and Mac OS X Leopard (10.5) disks - they're out there somewhere
Good luck cashbox mate x