It doesn't work on my G4 MacMini either (1 gig of memory, OSX 10.4.8, 1,33GHz PPC processor). When launching the application the screen goes black for a rather long time, then the cursor blinks for a fraction of a second (might be when the screen resolution changes) and after that the program just c...

How about getting the working wersion up on the official Frets page?

If you want more betatesters (and possibly even coding help) you could ask around at some Mac forums, for example the Finnish Omenamehu.