Ive found a reasonably cheap disc for 10.4.9 to upgrade my Power Mac G3 from 10.0.4, but i was curious if the disc being for a G5 has any impact on my ability to install on my G3.
I have to agree. You need to get a retail version of OS X. The discs that come with a Mac are for that model range only. It prevents pirating of their OS. It is a good idea.