5 open source tabletop RPGs you should try: 
Open source arrived in the pen-and-paper RPG industry back at the turn of the century, when Wizards of the Coast, publisher of Magic: The Gathering and Dungeons & Dragons, developed the Open Game License (OGL). Many publishers have since adopted the OGL themselves or use similar licenses, such as Creative Commons.
read more: Opensource.com sethkenlon
Supporting Open Source.
Have you tried: Farking?