As my DVD burner is attached my linux PC, and I can't burn on the iMac, I thought I should ask here too.
There are instructions at
http://creativebits.org/mac_os_x/make_a_dvd_copy_of_mac_os_x_tiger on how to create a bootable MacOS DVD on an iMac.
I've already tried burning the ISO image using NTI backup on XP, and that wasn't bootable, and my version of cdrecord on Suse 9.3 says its license has expired. (I haven't tried cdrecord on Suse 10.0 yet, but it'll take a while to dig that system out)
Are there some special options to cdrecord to make a DVD iMac-bootable?