Note: This does not cover whether to publish using the Open Game License (not every project needs to), nor the consequences & limitations (there are many!) of publishing using the OGL. This is only about HOW to deploy the OGL correctly, for when you want to or need to.
You must take four steps to deploy it properly, and the OGL itself contains instructions on how to do so:
Step 1 — Add a Notice to your projectFrom the OGL (note the bolded part):
“2. The License: This License applies to any Open Game Content that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License. You must affix such a notice to any Open Game Content that you Use. (snip)”
In other words, your published project needs to somewhere say “Open Game Content may only be Used under and in terms of” the OGL. You don’t have to use that exact quote though.
Here’s what I added to The Hyqueous Vaults (a recent free project I worked on that was published using the OGL) at the start of page 16:
The Hyqeuous Vaults contains Open Game Content, as defined in the Open Game License, below. Open Game Content may only be Used under and in terms of the Open Game License.
Step 2 — Add the OGL to your projectFrom the OGL:
“10. Copy of this License: You MUST include a copy of this License with every copy of the Open Game Content You Distribute.”
In other words, you must paste the entire text of the OGL into your project.
On page 16 of The Hyqueous Vaults, you’ll find the entire Open Game License, following the text that was added for Step 1.
Step 3 — Fill out the OGL Copyright NoticeFrom the OGL:
“6. Notice of License Copyright: You must update the COPYRIGHT NOTICE portion of this License to include the exact text of the COPYRIGHT NOTICE of any Open Game Content You are copying, modifying or distributing, and You must add the title, the copyright date, and the copyright holder's name to the COPYRIGHT NOTICE of any original Open Game Content you Distribute.”
This tells you two things:
First, if you Use (as defined in the OGL) any Open Content from other item published using the OGL, you must copy the Section 15 details from the other item, and put them into your own Section 15. Do this for every such item you Use. If you Use five other OGL-based items, you’ll have a lot of copying to do. If multiple Used items all have an identical line in their Section 15 (they all have this line, for example: “Open Game License v 1.0 Copyright 2000, Wizards of the Coast, Inc.”), you only need to include that line once in yours.
Second, you need to add a line to your Section 15 with the copyright info for your own project.
The Hyqueous Vaults, for example, Uses content from OSRIC, and the Sandman from the Tome of Horrors Complete. So I needed to copy Section 15 info from OSRIC, as well as the Section 15 info from the relevant parts of the Tome of Horrors Complete (which has some special instructions for how to reference individual monsters therefrom). Those sources’ Section 15s had lines for the System Reference Document and a couple Swords & Wizardry books, I copied those into my Section 15 too.
Finally, I added a copyright line for The Hyqueous Vaults itself.
The result was:
15 COPYRIGHT NOTICE
Open Game License v 1.0 Copyright 2000, Wizards of the Coast, Inc.
System Reference Document copyright 2000, Wizards of the Coast, Inc.; Authors Jonathan Tweet, Monte Cook, Skip Williams, based on original material by E. Gary Gygax and Dave Arneson.
OSRIC copyright 2006-08 by Stuart Marshall, adapting material prepared by Matthew J. Finch, based on the System Reference Document, inspired by the works of E. Gary Gygax, Dave Arneson, and many others.
Swords & Wizardry Core Rules. Copyright 2008, Matthew J. Finch
Swords & Wizardry Complete Rulebook. Copyright 2010, Matthew J. Finch.
Sandman from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene, based on original material by Roger Musson.
The Hyqueous Vaults Copyright 2017, Hyqueous Vaults Creation Team.
Step 4 — Identify your Open Game ContentFrom the OGL:
“8. Identification: If you distribute Open Game Content You must clearly indicate which portions of the work that you are distributing are Open Game Content.”
This means you need to add text that allows somebody else to understand what parts of your project are Open Game Content, so they can—in turn—use it in their own projects.
You can do this many ways, from a text description of what is Open Game Content, to using boxes around or colors behind Open Game Content, to anything else, so long as it's clear.
For The Hyqueous Vaults, I used a text description, and put it after the OGL on page 16:
DESIGNATION OF OPEN GAME CONTENTStrictly speaking, I didn’t need to designate what was Product Identity; the OGL doesn’t require you to that, and in fact has a pretty thorough definition of Product Identity already. But lots of publishers designate it anyway, because it allows them to clearly indicate what stuff is off-limits to people who want to otherwise Use some of the Open Game Content.
The following is Open Game Content, except as excluded by the Designation of Product Identity below: Spells, magic items (excluding whispering tome), creature statistics, the complete new monster entries for ur-ameboid, eel-man, sandman, and vodyanoy, and the complete new magic item entries for spectral candle, prime rod, shroud of the water striders, pointing key, thrice-blasting ring, and blossoming quffa.
DESIGNATION OF PRODUCT IDENTITY
Everything not designed as Open Game Content is Product Identity, including, but not limited to, artwork, maps, logos, layout, formatting, and the names The Hyqueous Vaults, Hyqueous Vaults Creation Team, Zirrind, Redbeck, Emanreh, and OSRIC.
SummaryIt is not sufficient to just paste it in the unmodified Open Game License and call it done; you always have to modify Section 15, include a notice, and include a designation of Open Game Content.
I have seen people simply not bother to read the OGL, and thus deploy it incorrectly, leaving themselves in breach of the license. Yes—the OGL is a legal license, so if you plan to agree to it, you should also read it!
For more details on the OGL, see Matt Finch’s OGL video series (starting with part one here), and Rob Conley’s OGL Primer (and be sure to read the comments, where I outline some consequences he missed).