Like Paul said, Rogue Amoeba is not required to release the source code if they are no longer distributing any GPL'ed code. That anyone would be forced to do so is a common misconception, one that is perpetuated by people with an anti-open source agenda ("Open Source is a cancer that will doom your proprietary product if GPL'ed code finds its way into it").

Thanks Quentin and Rogue Amoeba for the prompt resolution of this matter.