... which is a trademark license anyway.
There is no copyright possible on game mechanics, so you can pretty much write your own completely D&D compatible game, with the rules taken straight from D&D (but rephrased, of course, because the actual phrases are copyrighted). As long as you don't advertise this with trademarked terms, you're fine, you don't need the OGL.
But anyway. Who in his right mind would want to use this complicated mess as a base for his own game, when there is a system from 1978 that is much, much more elegant, named BRP? http://basicroleplaying.org/