Another thing to remember about the #OGL is how I think it was shaped by two events of the '90s.
First was the start of Wizards of the Coast. The Primal Order, their first product, resulted in a lawsuit from Palladium Games because they included conversion appendixes for a variety of RPG systems. (TPO was a "capsystem" product meant to be added on your game of choice.) This is exactly the sort of thing that people are now claiming is obviously fair use. It was not so obvious, Wizards well knew!