I release my work as free software mostly in the hopes that other developers will read the code, learn from it, and help improve it. In this case, the person has learned from it, claimed a number of my ideas as his own, lied about the rest, and now is going to take what he's learned to build something that he won't freely share with everyone. All of which I find deeply offensive.

None of what he builds would have happened without my decades of work. Beyond rude...