Lynn - that's not entirely true. Yale does the convention circuit and sells prints of his work. His web comic is free, but he is making money off prints.
http://yalestewart.bigcartel.com/I own "We Will Be Giants" (Just Clark and Bruce, I bought it before he did the entire Justice League) and the Superman/Batman Jim Lee Parody.
Maybe he has permission after all, if he's able to sell some of his work?