"Artists Beware"

If a commissioner states "I agree to the terms of this commission" in a note, than it can be considered binding - you don't need a signature. Even a handshake without verbal conformation can be held up in court as a binding contract. I'm a little iffy on the no refund bit, but in all honesty if the commissioner agrees, it doesn't really matter. Saying you wont refund money isn't illegal - though it is extremely bad business.