Don't take the prize and just release the code as open source and call it a day. That way, there's no way this asshole can claim work-for-hire (probably couldn'

Don't take the prize and just release the code as open source and call it a day. That way, there's no way this asshole can claim work-for-hire (probably couldn't anyway, but just to make sure) and at least he will no longer have anything proprietary. Or if you really feel like it, sue him if he actually uses the software, but it's likely not worth the additional time and money investment.