Comment by andolanra

There are a truly massive number of RPGs out there with a wide variety of open licenses, especially the various Creative Commons licenses. The indie RPG sphere is massive and includes tabletop systems that range from "mild variations on the core D&D formula" to "almost fundamentally alien approaches to doing structured role-playing". D&D has long-standing brand recognition and cultural cachet, but it hasn't been the only player in this space for decades.