Oh, here we go, Apple wrote about how to use DVD-RAMs and they can say it better than I.

http://support.apple.com/kb/TA44310?viewlocale=en_US

You can start up your G4 from DVD-RAM apparently, but it doesn't say anything about older macs starting up from dvdram drives. it may or may not be possible, but system 8.1 probably won't work, for reading/using the dvd-ram discs, or booting up from them.