Can I install leopard from the original DVD on a PowerBook with broken internal drive using a MacBook Pro?

You can install Leopard using a USB. First, you have to create a .DMG of the DVD on the MacBook Pro (Disk Utility>Click on the DVD>Click "New Image" and save it as what ever you want. Keep disk utility open and plug in a USB that is greater than 8 GB in capacity, click on the USB in the side bar and go to the partition tab, create a partition and go to the "Options", make sure you choose Apple Partition Map and then proceed to partition. Then go to the restore tab choose the .DMG that you created as the source, and chose the USB as the destination, click restore. Once this is finished, eject the USB and plug it into the PowerBook. Turn the PowerBook on and hold Command+Option+O+F this will take you into open firmware then type "boot ud:,\\:tbxi", then it should start to boot into the Leopard installer

Yes, a FireWire optical drive similar in useful purpose as the built-in combo or superdrive that

can read DVD and CD media, data and other content should be capable of using the system

install-restore disc as a boot disk so the installer on it can prepare the computer hard drive for

use with the OS X on the retail or the original grey-label software disc.

However not all FireWire external optical drives are guaranteed to perform this task, some

time has gone by since these were in vogue, so you may have to find & try other models if

the ones available don't work as expected. Also the reading lens in the optical drive may be

dusty or dirty, so a disc cleaner may be needed.

Hopefully you can restore usefulness to the older computer.

Good luck & happy computing! 🙂