Well, just to follow up, I've actually got my first release...

http://www.retards.org/projects/m68kmpc/index.php

... It's pretty basic, and only useful to those of us with older networked macs *and* mpd running on a server. Runs on 6.0.5.

Thanks to whoever said I should support system 6. You were right.

Thanks for everyone's help.

Nathan