Mark Pilgrim wrote on CSA2:

I just had a brief but constructive email discussion with Paul Lutus, the author and copyright holder of “Electric Duet,” the 2-note software synthesizer for the Apple II. He has generously agreed to release the music player routine itself under the GNU GPL. Paul requested that I credit it like this in my upcoming project:

Electric Duet Music Player
Copyright 1982, P. Lutus
Released under the GPL

Paul informed me that this open source license grant applies only to the player routine itself (the one you can tell Electric Duet to generate at any starting address and save as a separate file). The rest of the Electric Duet disk, including the editor, remains under his original copyright.

I don’t claim to speak for Paul. I’m just reporting the outcome of our conversation in a public forum in case anyone else is interested.