You're right, you're not going to get actionable legal advice on HN or from random articles you read on the Internet. The fact that the article cites precedent

You're right, you're not going to get actionable legal advice on HN or from random articles you read on the Internet. The fact that the article cites precedents only helps you when you are spending more money than you likely have trying to defend yourself from a lawsuit that will likely come. Whether or not you prevail in the end is immaterial; the momentum (and lawyer's fees) you lose will not be worth it. In other words: if you can't afford to talk to a lawyer now, you really can't afford to try to hold on to the source code. If it were me, I'd take a crack at trying to find an amicable (and written) solution with the guy; if that fails, I'd walk away and consider it an educational experience.