Open Game Systems
Roughly once a month, there's a thread on RPGnet asking about what systems are available under an open license like the OGL or the Creative Commons licenses. This project aims to collect all those games, ordered by license, on one page, to help aspiring game designers and publishers find an open system for their games.
Definition: What is an Open License?
So far I haven't found a simple and comprehensive definition of what exactly constitutes an "open license" in the general sense. The Open Source Definition, used by the Open Source Initiative, isn't really usefull in the context of RPG game rules, so here is my ad-hoc and a bit vague definition:
"An Open License allows the free and perpetual re-use of original material by anybody willing to follow the restrictions of said license, without an explicit contact or negotiatian between original author and licensee."
In other words, if something is available under an open license, I can use and re-use it for free, as long as I respect the restrictions laid out in the license, without having to ask or contact the author. (If somebody has a better definition, I'm all for it.)
Good examples of Open Licenses used for RPG systems are the Open Game License, the original Fudge License and various Creative Commons Licenses.
Many of those licenses are not compatible with each other, so people wishing to use material covered under multiple licenses should keep this in mind. (And probably consult a lawyer. Or at least the licenses FAQ.)
The List:
The following systems are available under an open license and are thus free to use in your own publications. (Though with varying restriction on the use of the material.)
Open Game License (Direct Link)
- BFRPG, Basic Fantasy Role-Playing Game.
- Modern d20 SRD
- d20 Anime SRD (direct link to file)
- Fate 2.0 (direct link to the file)
- Spirit of the Century
- Action! System
- Runic (Used in the Runequest RPG)
Open Game License and Another License These games release their material as Open Game Content, but also provide another, more restricted, license to allow publishers to refer to Product Identity.
- d20 System 3.5 SRD, Dungeons and Dragons (OGL and d20 System License)
- OSRIC (OGL and OSRIC Open License)
- Labyrinth Lord (OGL and Labyrinth Lord Trademark License)
- Mutant Future (OGL and Mutant Future Trademark License)
- GORE (OGL and GORE License)
- Wayfarers (OGL and open-ended agreement)
- Prometheus SRD (OGL and Prometheus License)
- FUDGE (OGL and FUDGE System Trademark License; also under its own license)
Creative Commons Licenses
- Drowning and Falling (Attribution/Non-Commercial/Share-Alike)
- The Shadow of Yesterday (Attribution)
- Donjon (Attribution/Share-Alike)
- Wushu Open (Attribution)
- Wushu Open Reloaded (Attribution/Share-Alike)
- Shadows (Attribution)
- Myriad (Attribution)
- Violence (Attribution/Non-Commercial/Share-Alike)
- Star Wreck (Attribution/Non-Commercial/Share-Alike)
- Noteworthy (Attribution/Non-Commercial)
- Executive Decision (Attribution/Non-Commercial/Share-Alike; direct link to file)
- ...in Spaaace! (Attribution/Non-Commercial/Share-Alike; direct link to file)
- Violence (Attribution/Non-Commercial/Share-Alike)
GNU free documentation license
- Gods and Monsters
- Circe (also GNU General Public License)
Other
- 4C System (Public Domain; Direct link to file)
- Dominion Rules (Dominion Rules Licence)