Jester David
Hero
In terms of roleplaying games? There are 3rd Party books for Pathfinder, Vampire, and several others. Plus fan sites.I am confused. What other games exist out there that have any sort of 3rd party material released for them?
For games in generally, you can buy 3rd Party video gaming accessories. Like different console controllers and the like. And I've seen unofficial board game expansions.
Just like you can customise your car, iPad, iPhone, action figure, assault rifle, bike, etc with optional add-ons that aren't supplied by the manufacturer and are just listed as "compatible".