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?
There is no simple or comprehensive definition of an "open license". The Open Source Definition, used by the Open Source Initiative, isn't useful in the context of RPG game rules. This page operates under the following 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 negotiation 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.
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.)
Secondary Licenses
Many games, particularly those published under the Open Game License, also include a secondary license which allows the publication of compatable material using the trademarks of the game. These licenses restrict the publisher further than the OGL does, and sometimes include requirements that do not qualify as an open license. For example, Mutants & Masterminds is released under the OGL, and also under M&M Superlink. Superlink is not an open license - it requires potential publishers to contact publisher Green Ronin for their project to be approved. Mutants & Masterminds is still listed on this page because its content is under the OGL, though its trademarks are not.
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, Runequest RPG
- Iridium System
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)
- Swords & Wizardry (OGL and the Swords & Wizardry Compatability Statement License)
- Mutants & Masterminds (OGL and M&M Superlink)
- True20 (OGL and True20 Adventure Roleplaying Trademark 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)
- Action! System (Action! System Open License)
- Active Exploits (Active Exploits Distribution and Expansion License)