Back in the early 2000s, when D&D was quite successful the whole RPG industry was getting on board the OGL and making d20 products. Even unrelated products had a chapter for playing the game with d20 instead of the system in the book. And, given these things are true I see no reason to think I'm better than them. I would have made this a chapter of my book, but it requires me to paste the license in there to use it so I didn't. Instead it is a separate free product. Check it out. It's good for a laugh if nothing else.