Although this is a very old thread, it seems to be the only one of its kind, so I dared to reply anyways.
Did you in the meanwhile have any success with this? I am currently also looking for a SF2 and DLS reader in order to implement a basic minimal GM Synth that can replace Apple’s DLSMusicDevice (which is apparently no longer supported on 10.7. At least the playback volume is extremely low and cannot be changed).