Does development on this application continue, outside of what hobbyists and enthusiasts like Cosmos push forward? 'cause 7+ years with no release sounds like abandonware, to me...
There is no such legal construct.
I'm job less and I have no money to give, sorry...
This is a woefully facile argument, one I tire of reading over and over again. With the number of community-funded bounties, Kickstart and IndiGoGo projects out there, not having money for a particular project is a non-starter. In fact, repeating it every time someone criticizes your work* seems like you are fishing for sympathy.
If Developer X wants $Y for someone to take over his or her rights to a particular product, there is no reason not to run over to Amiga.org, EAB, AA, and others to put up a post saying "Hey, I want to improve Product X, and the developer wants $Y for the rights. If you want to see this great product supported by a great active developer, please donate here!"
If Developer X ignores you or is otherwise not open to your advances, then a public post about the issue could elicit others to step in and advise or assist. At the very least it could open an underground of support for your project.
* To be sure, I understand your work to be heartfelt and by many accounts very good; a true labor of love. I, for one, appreciate you are willing to tackle the problems, though I believe, as others have mentioned, a better approach exists to disseminating your work.