Let's take a moment to talk about the uses and value of a system reference document to a game designer. This post will focus on system reference document licensing.
I'm working on my system reference document. I've also made a few games based on SRDs, including one I'm working on right now.
An SRD is a core of rules for a game that can serve as the foundation for a larger project.
This post talks about licensing, but there are also partner posts on types of SRD and the reasons to use SRDs.
I should point out before I go further that most of the SRDs that I will discuss are freely available and operate on an open license. Usually this is the Open Gaming License or a Creative Commons license.
I don't use either, but both are tolerable. I cross-license my work under CC-BY.
The license for an SRD determines how and why people will use it. If an SRD is not under an open license, other people can't (legally) make games with it.
There are a couple reasons to do this, but they're not why most people make SRDs.
I won't discuss all rights reserved SRDs' licensing. They're occasionally licensed out (e.g. for DriveThruRPG's community content marketplaces). However, this involves arcane discussions of individual cases in trademark and copyright law and licensing.
Even if the terms are fairly straightforward, the arrangements are atypical and unique per-system and I can't cover all of them.
The OGL is not very layperson friendly. However, its outcomes are benign. You can use OGL content for anything, so long as you have some disclaimers and notices attached. The downside is that these notices are, again, not terribly legible.
The OGL is best known for D&D and Pathfinder. D&D and Pathfinder-derived SRDs typically excise non-OGL content, making them ideal for avoiding complications. OGL licenses often apply only to some parts of a book.
The OGL comes from tabletop games. It is liberal, non-viral, and has no legal complications. It's the guy in a suit of SRD licenses.
A key advantage of the OGL is that it aligns well with US trademark and copyright law, with wording that lets you pick exactly what to license and protect trademarks while opening copyrights.
But the OGL, despite its liberality, is scary, and at least as written obligates the reproduction of the license text in entirety. This means a page of ugly legalese somewhere in your book and all derivatives. And the OGL's tight legal language defies typographical standards.
Creative Commons (CC) offers a range of licenses. The least odious kinds are the CC0 public domain license and the CC-BY attribution license, and the more tags it has the less free it is. The CC-ND license permits redistribution, but not derivative works, which is an exception to this rule.
CC is popular because of its broad adoption across creative fields. It's also more human-friendly than the OGL.
The Creative Commons tends to lump in trademarks, which leads to some interesting potential issues. Another issue with the CC licensing scheme is that some of the non CC0 versions had rules about encrypting or otherwise applying digital rights management to content, which has the significant negative consequence of creating inadvertent liability.
You won't run into this 99% of the time, and I don't think it's ever been enforced. The only case I can think of where a TTRPG creator would run into issues with this would be if you were using a licensed asset on DriveThruRPG in a protected PDF, but this is so astonishingly rare that I don't worry about it. It's intended as a way to prevent you taking an asset and using it while keeping it unavailable to others.
If you're not doing that, the CC people won't come after you, and most rights-holders don't care enough to or aren't aware of that clause in the CC.
However, this is a reason I always dual-license my work under a non-CC and permissive license.
Before continuing, I want to go over what the CC tags mean.
Public domain licenses basically say you don't have any objection to anyone using the content.
This doesn't obligate any user to do anything after using your work.
There are several repositories of CC0 content, such as Pixabay and Pexels, which can even be useful for game designers. The image below comes from Pixabay.
I still suggest crediting CC0 content because it can save you some legal headaches down the road. The nice thing is that it's just providing a source–legalese is optional.
Make sure that any CC0 content you use doesn't include trademarked or copyrighted elements not relevant to the work itself. If there's a photo of a Manhattan street that features an ad for a movie, that ad has its own copyright. That may or may not be an issue, and I'd seek legal guidance (or just use CC0 content that doesn't include other artistic works in the broad sense copyright law defines it).
I don't know of anyone using CC0 for games, but it's totally possible if that's your druthers.
This license requires you to give credit, and there are a few boilerplate ways to do so. We won't worry about those here, since the attribution text is usually included (and will be in the SRDs I reference in a moment).
CC-BY is non-viral, meaning that you don't have to license your work under CC-BY. You can reserve all your rights to a derivative work.
That means that you can sell it, refuse others the right to distribute or alter it, and otherwise hold on to it.
I consider CC-BY the ideal of Creative Commons licenses, and it's the foundation their more restrictive licenses build on. I won't go over all the configurations, I'll just talk about what the tags mean.
The Non-Commercial licenses permit commercial exploitation of a work.
That is, you can't use NC licensed content to create anything for profit.
I'm not sure exactly how the boundaries fall here, but I treat anything with NC as basically having all rights reserved because I make money off of my games. This means that someone could claim that I made a game based on NC content to promote my other work. This would probably not hold up in court, but I ain't getting sued over it.
Although NC licenses are theoretically non-viral, I'm not sure how that would work in practice. I consider the non-commercial clause to be legally dubious. It is definitely binding on end users, and I would avoid using it out of prudence.
Share-Alike licenses can combine with Attribution or Non-Commercial licenses. This adds an explicit viral element, saying that users must license all derivatives in the same way as the source material.
This does not mean that you can't make money off of your work (unless paired with an NC license). You can make and sell content under a CC-BY-SA license, but you cannot enforce copyright claims on it.
It means that anything you make has to be licensed identically. You cannot remove or add to the license.
There is an open question on whether CC-BY-SA has to apply to a whole work or just the derivative parts. For instance, if the rules text of a game used CC-BY-SA content, it might suffice to make a plaintext version of the rules freely available but restrict the distribution of visual elements. I would consult a lawyer and/or the original creator of the content about this.
I avoid using SA-licensed works, but there's nothing legally problematic about them.
This means that the work itself cannot serve as the basis for derivatives.
You can distribute an ND-licensed work. You can even sell the work, assuming it doesn't have an NC-license attached.
The question of what legally makes up a derivative is interesting. If you included a work wholesale, or in a naturally cut-down framing (e.g. 30 seconds of a song playing in the background), this might still constitute a derivative in a legal sense.
As a result, I would avoid including an ND work, even if you might have a tenuous legal case that you did not make a derivative. Using this for an SRD would mean that you are creating a freely redistributable, but not freely usable, rule-set for people to pass around.
I use a very simple license for the Initiated SRD:
“This work is based on the Initiated System Reference Document by Loreshaper Games. Use of the Initiated SRD does not imply their endorsement of this product. Maintain this notice in any derivative works.”
I also double-license under BY-SA 4.0 which has similar effects but less clarity.
Compare this to the following license for the Kenoma Quick Start, which isn't an SRD but aims to allow (limited but generous) use.
You can freely distribute this book so long as you include the About, Credits, and License section that make up the front matter. The following terms apply to the creation of any derivative work:
You must include the following notice:
“This work is based on the Kenoma Quickstart by Loreshaper Games. Our use of their work does not imply their endorsement of this product. Maintain this notice in any derivative works.”
Loreshaper Games reserves the sole rights to use the Kenoma title for their products, though you may create your own products labeled as “Compatible with Kenoma” so long as they maintain this notice and the above notice.”
You may distribute (and sell) your own derivative works so long as they do not:
1. primarily repackage text, art, design elements, or intellectual property such as characters and setting elements from an existing product
2. feature images from Loreshaper Games products not cleared for third-party use by Loreshaper Games
3. violate other legal restrictions (e.g. using copyright infringing material from third-parties)
We also reserve the sole rights of distribution for our own Kenoma content (except where otherwise noted in the first part of the license section), in digital and print formats. However, We do not make claims against the resale of physical products.
We are not interested in prosecuting those who share digital versions of our products with their play groups. If you have received this product in this way, please consider purchasing it from one of our supported marketplaces so that you receive the most up-to-date version. If you have any concerns regarding the license or wish to make special arrangements to use content outside the scope of this general license, please reach out to us!
This is not an open license, but permits people to make derivatives and associated products that reference our work and imposes no restriction on them doing so. It wouldn't be ideal for SRD licensing, but it's not a terrible idea either.
A system reference document's licensing terms make it useful or render it worthless for users and creators alike.
A more liberal license, such as the Creative Commons Attribution license, is ideal for most use cases. This lets people take an SRD and work on it directly, keeping the whole text.
The OGL is equivalent to this license, if a little more unwieldy. I suggest the OGL if you want a more granular control over what you release (e.g. rules text versus illustrations), since the legalese has built in functionality for that.
One consideration here is that Creative Commons licenses assume works are complete.
With a roleplaying game book, this may not be the case. If you are taking some works from the public domain, some from artists under contract, and some you own, you can run into complications. For instance, if you use stock art, you need to make it clear that you are not opening up rights to reuse that work.
An SRD often gets around these questions by including just CC or OGL content. That way, everything is good to use. As a designer working on a game that you want to license openly, having a separate SRD can accomplish that goal without running into issues with rights for your other content.
It's more work, but also has significant advantages.
Pay attention to the fact that many custom licenses may specify different terms. For instance, the Kenoma license lets you take stuff and reuse it, but is specific about how you market it.
Check out the following articles for more information on SRDs:
The Art of the System Reference Document: Types
The Art of the System Reference Document: Uses
