[Jarwain]

Did he not honor the informal agreement?

To me the agreement sounds like they bought the right to use the story as the ending to the game. They didn't agree on signing over the rights to the story, and he said if he knew that would have been part of the deal he wouldn't have agreed. He was caught by surprise when he found that language in the contract. Sure he was negligent in not following up when the contract didn't match his expectations, but so was Mojang for not ensuring the contract was signed before using his work.