So I finally aquired a copy of 10.4, installed it on my aging B&W and love every second of it. I wanted to try it out on my iBook (which is only slightly faster) but the combo drive is dead. I know that you can use a firewire cable to direct boot off of another system, but could I do this to update the OS? At this point I've come to grips that I'm stuck at 10.3.9 but I still dream...
Recent Macs (at least the Mini, didn't test other systems) not only export the hard disk in Firewire target disk mode, but also the optical drive. I'm not sure which models exactly support this and couldn't find a list.
If you want to use your B&W to upgrade your iBook, this method most probably won't work. One idea to get around that limitation would be to copy the 10.4 install DVD onto one of the G3's hard disks and try to boot from this. I'm not 100% sure if this will really work.
Of course, you could also use an external Firewire CD/DVD writer to boot your iBook, those are quite inexpensive these days.
I'm not sure I understand correctly, but you're saying you want to put Tiger on the iBook and update the 10.3.9 install already on the iBook?. Assuming you have an iBook with Firewire and the B&W G3 with a DVD reader of some kind then it's really very easy.
Put the iBook in Firewire Target Disk Mode. Boot the B&W of the Tiger DVD, and then install onto the iBook.
Another way to do it, and this is what I used to do every other week to sync my iBook G4 with my Digital Audio until I got a MacBook Pro, is use SuperDuper and just clone the B&W onto the iBook (you might want to use the migration assistant to migrate data off the iBook onto the G3 first).
Hope that helps.