Ouch. I was about to recommend a G4 iMac-using family member to upgrade to the recently released iLife '08, but then read its system requirements:

iMovie requires a Mac with an Intel processor, a Power Mac G5 (dual 2.0GHz or faster), or an iMac G5 (1.9GHz or fast

It also needs OS X 10.4, which eliminates this family member's computer on two counts.

In any event, this "completely redesigned" iMovie shows that, at least in-house, the G3 and G4 are D-E-D [sic] dead to Apple. In the latter case, that seems a little quick.