G4 files moving to 10.6.8
I'd recommend that you use Firewire target disk mode.

From article "How to use and troubleshoot FireWire target disk mode" (http://support.apple.com/kb/HT1661):


  FireWire target disk mode allows a Macintosh computer with a FireWire
  port (the target computer) to be used as an external hard disk
  connected to another computer (the host). Once a target computer is
  started up as a FireWire hard disk and is available to the host
  computer, you can copy files to or from that volume.


You basically need to:


Connect both computers with a Firewire cable.
Start your G4 Mac while pressing the T key until a FireWire icon appears.
Wait until a firewire drive icon appears on your MBP's desktop. Open the drive and copy what you need (probably in /Users/&lt;your username&gt;).
When you're done, eject the drive as usual (⌘E or drag it to the recycle bin) and power your G4 Mac off.