June 2109 Update: Many notable things have changed since this article was first published. An updated version is in the works. I swear.
There are varying reward tiers depending on your support level and the type of supporter you are (gamer, publisher, etc.)
The History, Current State of OGL Publishing, Pathfinder, and "d20"
The Open Gaming License and d20 System Trademark License were first released in 2000. Since then, other trademark/compatibility licenses for other systems and games have been created, and the use of other open licenses has proliferated.
The Open Gaming License still remains popular (while the d20 System Trademark License was retired in 2008), however most OGL material published in recent years (2010-) is geared towards being support material for the Pathfinder Roleplaying Game under the Pathfinder Roleplaying Game Compatibility License.
This article explains the history behind these various licenses, along with some guideline for how they can be used in publishing.
Open Game Content: Material that is specifically licensed under the Open Game License, created by Wizards of the Coast.
Product Identity: Material included in a book that includes Open Game Content that is specifically defined by the publisher as not being OGC.
Third Party Publisher: A publisher creating material that is designed to be compatible with another publisher's game; most commonly used to refer to d20 System- or Pathfinder-compatible product.
Which was the First d20-licensed book?
Green Ronin's Death in Freeport, Atlas Games' Three Days to Kill and Necromancer's Games' PDF The Wizard's Amulet hit the ground on the same Gen Con weekend as Wizards of the Coast's Dungeons and Dragons Player's Handbook did in 2000.
Three Days to Kill was locally available at The Source Comic and Games in the Twin Cities, Minnesota in the week before Gen Con.
What's an SRD?
SRD refers to System Reference Document: often a Rich Text or HTML document that only includes Open Game Licensed material, designed to be used by a publisher as a starting point of reference or a manuscript. By using vetted System Reference Documents, publishers could help ensure that they were only OGL material.
Wizards of the Coast released multiple System Reference Documents (For 3.0 and 3.5, and d20 Modern), as did Guardians of Order (Anime d20).
Paizo maintains a SRD for Pathfinder called the Pathfinder Reference Document, and there is a SRD maintained by the public at at http://www.d20pfsrd.com/ which also contains some material from 3rd Party Pathfinder publishers.
It has always been recommended that if you wish to produce material based on Open Game Licensed material, that you only refer to SRDs whenever possible, as opposed to mining material from printed books.
The Open Gaming License
The first thing to understand about the Open Gaming License is it is not designed specifically for any one gaming system. Anyone can write material and place it under the Open Gaming License. However, most commonly the OGL has been used to re-use material placed under it by Wizards of the Coast: the 3.0 and 3.5 SRD, and the d20 Modern SRD.
As far as content licenses go, the Open Gaming License is incredibly simple (it's shorter than this article!). It allows you to re-use and modify material that has been placed under it, and also allows you to intermingle that Open Game Content (OGC) with closed content, which is described as Product Identity. This allows you to, for example, use monsters from the SRD in an adventure, with you declaring that the "flavour text" descriptions of the other characters, events, and locations in the adventure are your Product Identity.
One of the conditions in the OGL (Section 7) does not allow you to use anyone else's Product Identity. Be aware that simply using the name of a Wizards of the Coast-published spell or monster that is not included in the System Reference Document may cause you to run afoul of this clause. This includes using that Product Identity "as an indication as to compatibility"—which means you cannot (without obtaining permission otherwise) indicate that your product is compatible with Dungeons & Dragons, Pathfinder, or any other game title, trademark, etc. The full list of what is considered by default to be Product Identity is listed under section 1 of the OGL.
Beyond not including material that you cannot include under the OGL in your product, the most important legal aspect of publishing something that includes OGC is Section 6 and Section 10, which stipulates that you must include a copy of the Open Game License in your product, and you must correctly add to and update the Copyright Notice portion of the license to include the Copyright Notice from any Open Game Content that you used in your product, and also append your own Copyright Notice to it. This section is numbered as Section 15 and often referred to as such.
In order to prevent problems, you should keep careful track of when you sourced OGC, and where you sourced it from, and save their Copyright Notice / Section 15 verbiage so you can include them in your own product.
Of course, the OGL has further clauses to it: you need to read and understand the entire thing before using it. If you find portions of it difficult to understand, I suggest you look for similar projects and see how they handled things, and if you need clarification after that, try to speak to the creators of those projects.
If you are attempting to re-use something that you believe may be Open Game Content but aren't sure if it is, or if it's Product Identity, ask the publisher of that project. Assuming that something is Product Identity is always safest.
The Open Gaming License is irrevocable: if you place content under that license, it is perpetually under it.
The full text of the Open Gaming License: https://web.archive.org/web/20030604210922/http://www.wizards.com/d20/files/OGLv1.0a.rtf (This is Archive.org's copy of the original license from Wizards of the Coast.)
The d20 System Trademark License
The d20 STL allowed publishers, if they adhered to more stringent rules, to place a d20 System logo on their book, and also to advertise compatibility with Dungeons and Dragons Third Edition, d20 Modern, and a few other Wizards of the Coast titles.
As the d20 System Trademark License is no longer available for use, the details of those restrictions and benefits are essentially irrelevant at this point.
d20 STL Revocation
In June 2008, Wizards ceased allowing publishers to use the d20 System Trademark License. Publishers with print books were granted a six-month period to sell off remaining physical stock, and six months to remove any electronic books from the marketplace, or modify them to be OGL-compatible.
Some publishers re-branded their books, creating a handful of new logos/brands to identify them as OGL and former d20 titles—but none of those new brands obtained widespread traction. As of early 2015, many d20-licensed books still exist in PDF form with minimal or no modifications to their branding or content.
Game System License (D&D Fourth Edition)
The GSL was announced in August 2007, launched in June 2008 and revised in February 2009. It was not widely adopted by third party publishers with many—including d20 stalwart Green Ronin Publishing rejecting it for being too limiting and too focused on serving Wizard's of the Coasts needs.
With D&D Fourth Edition's relatively short lifespan and lack of third party products, the GSL's legacy isn't in what it created directly, but what it created indirectly: Pathfinder.
If you are interested in the history of Pathfinder and Paizo, I recommend reading Paizo's 10th Anniversary Retrospective, available here: http://paizo.com/paizo/blog/tags/paizo/auntieLisasStoryHour—it goes into great detail on the company's history.
For those who want to publish material that is compatible with Pathfinder, you can do so in two ways:
Use the OGL
Pathfinder material is published under the Open Gaming License, as it is derived from the 3.0/3.5 SRD (amongst a few other sources). You can use the Pathfinder SRD to create derived and compatible works as long as you follow the Open Gaming License. However, this does not give you the right to use the Pathfinder name or any other trademarks (as they are Product Identity).
Paizo Inc. Pathfinder® Roleplaying Game Compatibility License
This license allows you to use the Pathfinder Roleplaying Game Compatibility Logo on your product, and to indicate compatibility with Pathfinder and refer to specific Pathfinder books. You are still required to use the OGL if you include any OGL content, and obey all of its clauses regarding Product Identity, Section 15, etc.
Paizo requires you to submit an application for the Compatability license, including a description of the products you intend to make.
Beyond that, the following page outlines the major facets of the license: how you can refer to Pathfinder and different Pathfinder titles, how you may and may not display the logo, etc: http://paizo.com/pathfinderRPG/compatibility
Paizo also maintains a Frequently Asked Questions list: http://paizo.com/pathfinderRPG/compatibility/faq
Old School Movement / Retroclones
An unexpected result of the Open Gaming License was the resurgence in availability of material that was compatible with prior versions of D&D. Multiple publications used the Open Game Content in the SRD to essentially recreate older editions of D&D and several of those rules sets have been further supported with original adventures and other content—essentially creating one (or more?) ecosystems that harken back to the style of rules and source material of the late 70s and early 80s!
Other OGL Material
Notable fantasy material licensed under the OGL, beyond Pathfinder, includes 13th Age from Pelgrane Publishing and Fire Opal Media. It has a Compatibility License: http://pelgranepress.com/site/?p=14447
Mutants and Masterminds from Green Ronin publishing is one of the longest running complete OGL games, having spanned three editions. It has a compatibility license, Super Powered by M&M: http://mutantsandmasterminds.com/licensing-mutants-masterminds/
Spycraft from Crafty Games has a compatibility license, Powered by Spycraft: http://www.crafty-games.com/licensing/spycraft
The Open Gaming License has been applied to other games and gaming material beyond the "d20-derived" style of gaming born from Dungeons & Dragons Third Edition. This includes Traveller from Mongoose Publishing, the GUMSHOE System by Pelgrane Press, Fate from Evil Hat Productions (which is also available under a Creative Commons license), and Fudge from Grey Ghost Games. Fudge is notable in that it was first published under a license of the author/publisher's own devising, and years later was placed under the Open Gaming License—which allowed Evil Hat Productions to truly move forward with the Fate gaming system which was originally derived from Fudge.
Of further note is the Open D6 system, from West End Games. The D6 system first appeared in the Ghostbusters RPG and was later used in the first licensed Star Wars RPG. Decades later the system was released under the Open Gaming License as OpenD6, after a second incarnation of West End Games failed to capture the market with their revamped series of D6-based books.
Licenses other than the OGL
Roleplaying games and sourcebooks have also been published under various Creative Commons licenses, but not all of them allow commercial re-use.
A few other licenses, such as the GNU Free Documentation License, have been used on occasion, and some games—such as Fudge, before it was licensed under the Opening Game License—had their own licenses designed to be used by one game only.
Trademark licenses without Open Licenses
There are also a number of games that allow you to publish compatible material with a compatibility logo, but that do not have any open licensed content for you to re-use, or any requirements that your material be open-licensed. This includes Pinnacle's Savage Worlds: https://www.peginc.com/licensing/
and the Hero System from Hero Games.
Creating Open Content in 2015 and Beyond
If you have the freedom to choose a license for all-new material, I suggest that the following considerations are the most important:
- Is the license appropriate for the type of material you are going to publish? The Open Gaming License was specifically designed for the text of a gaming book. Creative Commons licensed are aimed at mixed-media works: text + art + design, but you can use a CC license to only license part of a work—such as all the text or all the art or "all of chapters 15, 16, and 17" while not touching the remainder of the work.
- Does using the license grow the audience for your material—does it give you access to a community of fans?
- Does the license make your material available to use to others in ways that you find acceptable?
- If you have bought or licensed work from others to appear in your material (artwork, writing, etc), does the contract you bought/licensed it under allow you to republish the material under an open license? Most publishers buy material from authors and artists under Work For Hire contracts, and thus the publisher owns the copyright and get choose to re-license the work under any open license they choose. Ethically, people creating work that you publish should be aware that you plan on open-licensing it, too!
The following are my personal suggestions for how to license material. Please read and consider the licenses carefully; what is right for one person/organization may not be right for others. What is right for one project may not be right for your next project, either!
—If you want to create material for a game or setting that uses a specific license, use it.
—If you want to create a new game, not dependant on material already under one of the existing open licenses, use one of the Creative Commons Licenses. These licenses don't have the d20/fantasy/D&D implications that the OGL tends to have, and can allow for no commercial re-use, no derivatives, etc.
—If you want to create a new game, not dependant on material already under one of the existing open licenses, but with plenty of open-licensed material available to be used with it or converted to be used with it, use the OGL.
—If you want to create fantasy material with the widest possible commercial audience, produce material under the Pathfinder Compatibility License.
—If you want to create fantasy material with some degree of built in audience, but want the least restrictive license possible, use the OGL.
Publishing your own SRD
If you are releasing a lot of open licensed content, you should consider releasing it in a System Reference Document style. While originally publishers such as Wizards of the Coast and Guardians of Order released SRDs in the universal Rich Text Format, most are now released as web pages—usually using wiki software so they can be edited and amended by the community. Some SRDs are created and maintained entirely by the fan community.
Releasing a SRD will encourage people to use your material for their own works, as it will make it even more clear which material is available to be re-used.
Thanks to the backers of my Patreon project for helping fund this article, including, but not limited to: Brian Allred, Tara Brannigan, Jeff Eaton, Eleanor Holmes, Andrew Kenrick, Adam Tinworth, Lester Ward, Evil Hat Productions, and Melior Via.
In particular, thanks to John Dunn, Ryan Macklin, Craig Maloney, and Lester Ward for feedback on the initial draft of this article.
Special thanks to Jason Jensen for editing and access to his extensive collection of d20 titles.