D20 System

The d20 System is a role-playing game system published in 2000 by Wizards of the Coast and originally developed for the third edition of Dungeons & Dragons. It takes its name from the twenty-sided die at the center of the core mechanics of many actions in the game. Much of the system was released as the System Reference Document under the Open Game License as Open Game Content, which let commercial and non-commercial publishers release modifications and supplements without paying for the underlying intellectual property, which Wizards of the Coast owns. The open licensing was driven partly by the economics of publishing role-playing games, where supplements sold far worse over time than core books, and Ryan Dancey, the brand manager for Dungeons & Dragons at the time, directed the effort through the d20 System trademark, which is distinct from the Open Game License itself.