@bobjonkman Since the contract was illegal, the customer never got the right to the parts the developer wrote, I think, but he did get the rights to the GPL’led parts - so no passing on of the proprietary parts. I guess that the customer can then sue the developer for misleading or so, and part of the settlement could be that the proprietary code gets licensed under GPL, too - after all the customer paid for getting the program. But even though I read up much on that: IANAL. Or the customer could contact a copyright holder of the GPL code and notify him or her of the license breach. That could then get pretty nasty for the dishonest proprietary developer.