Hello,

> I recently got myself an iBook G4 12" and would like to try NetBSD on it 
> - preferably without repartitioning.
If you have a UFS partition you can put NetBSD there, that's what I did.

> Is it possible to install NetBSD on a USB or Firewire HD and boot it 
> from there?
In theory - yes. The firmware can boot from USB or FireWire devices. For me it didn't work because the kernel wouldn't reliably recognize my USB disk (an USB-IDE part) on startup so I couldn't use it as root, maybe it works for you though.

good luck
Michael