Rather than just totaly dumping it to the trash why not GPL it so others can legaly finish and improve what you left off.
I will add my voice to this request. Of course, there is the possibility that this will simply go underground, if it has not already done so. The saddest thing of all is the continuing reputation hit on the rather shady middle men in indy market (no reflection on the developers intended). GG and the lawyers need to get the hell out of the way of life cycle events.
I hope it works out well for us all. Intractable is such an ugly position. Particularly for those of us that invested in the model.
Be well. If you can not fully release, perhaps you will consider alternatives?
The ideal answer is yes, GPL, CopyLeft, or something similiar.... however, negotiation begins with not saying no...

Regards,
Rich