bedir than
Full Moon Storyteller
again, this is answered.Except neither of those use "withdraw" as a term, meaning that they don't address that particular point. (My saying that, it should be clear, is a reference to how the OGL could obviously not be revoked, and yet WotC's threat of doing so was based around the idea that it didn't expressly say it was irrevocable.)
Actual lawyers wrote this