If you did not sign anything, form a corporation or have anything written down, then it's an easy one: You can leave with all the code. I don't see how he could

If you did not sign anything, form a corporation or have anything written down, then it's an easy one: You can leave with all the code. I don't see how he could win in a court of law without legal documents. A promise/intent is not enforceable without proper signed documents. However any kind of litigation might cost you.