I realize that the GSL will not be the OGL. They will be different licenses. That's true. But, that doesn't make 4e closed. The GSL, apparently, will be a true reference document, without any of the text. So, if you want to publish a 4e module, you can by the GSL because you can reference the references (See Page X in Book Y), but, what you can't do is republish the actual content.
So, yeah, it sucks if you want to make a derivative game off of 4e. It's likely not going to happen since you can't reprint the text. But, for support material - new monster manuals, modules, whatever, it's just fine.