If the weights are not copyrighteable, you don't need a licence do use them, they are just data. There's not a right to infringe if these numbers have no author. Of course, to use openAI API you must abide to their terms. But if you publish your generations and I download them, I have nothing to do to the contract you have with openAI since I'm no part of it. They can't impede me to use it to improve my models.