At the time of this writing, Wizards of the Coast was attempting to unjustly, and probably unlawfully, revoke the Open Gaming License. They've recently agreed to stop that attempt, and as a sign of good faith they've released the System Reference Document (SRD) into Creative Commons. That's a minor victory for D&D publishers, but it doesn't erase what's transpired. By now, it's clear that Wizards of the Coast cannot be trusted, and it's easy enough for many players to stop spending money on D&D™ products because there are plenty of third-party products out there.
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I use a lot of third-party or independent content, and ironically I mostly bought Wizards of the Coast products in a conscious effort to support the company that maintained the game. Now there's every reason to not support that company, not only because they're seeking to end a longstanding agreement with its community, but also because they're actively working to erode the solidarity of gaming groups around the world.
There are hundreds of games and adventures and supplements and source books out there that were never obligated to use the OGL. They were written from scratch using original language, never borrowing from a System Reference Document in any direct way. Just as there were lots of roleplaying supplements back in the 80s that happened to work with that one game by TSR, these books are independent material that often happen to work with existing systems. But authors chose to use the OGL 1.0a because we recognized that sharing ideas, mechanics, and content was what tabletop roleplaying is all about. It's what it's always been about. Getting together with friends, some old and some new, and inspiring each other. That fellowship extended to the computer screen once digital technology and its infrastructure got good enough to facilitate extended video and voice calls, and to provide emulated tabletops, and so the pool of potential friendships got even bigger. The OGL 1.0a was a document you could copy and paste into your book as a sign that you wanted to collaborate. You were inviting people to your writer's desk and to your gaming table.
For a lot of gamers, the Open Gaming License 1.0a also defined the word "open". Being open is different than what we're used to. There's a lot of implied openness out there. Sure, you're allowed to dress up as your favourite Star Wars character until Disney says otherwise, and maybe you can write some fan fiction based around your favourite TV series as long as you don't sell it.
But the OGL 1.0a tells you exactly what you can use, and reference documents provide rules you can freely copy and paste into your own work, and then other authors can use your content to build up something cool. And nobody's restricted from selling their work, so it literally meant people could turn their hobby into their day job. And nobody could take that away.
And truly, nobody can take that away. But apparently none of us can say that until a court of law confirms it, and nobody exactly wants to go down that path. It's OK because we have replacement licenses, and Paizo is working on another one specific for gaming systems.
But the real damage, for the most part, isn't actually just aimed at content creators. It's being directed at the entire community. Before Wizards of the Coast stepped up to unjustly (unlawfully?) revoke the Open Gaming License 1.0a, the word "open" meant something in the gaming community. It already means something in the software world, and that definition is fiercely protected by organizations like the Opensource Initiative. But to gamers, that definition was a function of the Open Gaming License 1.0a, and Wizards of the Coast is trying to steal that term, and to redefine it as something...not at all open.
The fact that Wizards of the Coast is "revising" the Open Gaming License instead of just inventing a new license, as they did for 4th Edition, is in my opinion a supremely calculated move. They know the community values the ability to share resources, but they're trying to lock that community into a space owned by Wizards of the Coast. You have to pay to get in, and then pay a tithe to stay in. It's the opposite of open. It's literally closed, restricted. But they put a sign on the door that says "open" and they're hoping people believe it. As of their latest version of a license, they're using an actually-open license (the Creative Commons BY-SA International 4.0) on content that's already not copyrightable as a way to suggest that there is some openness happening. But that kind of openness is the same kind of openness that allows me to invent a new variant of Poker or Chess.
Wizards of the Coast has withdrawn from tabletop roleplaying. They've made authors and publishers doubt the safety of an open license.\ They've probably made a lot of players hesitant to invest in something labeled "open", for fear that it can be taken back at any time. A truly open system is by nature irrevocable, and the fact that Wizards of the Coast is threatening to take away a license they promised was perpetual says a lot about unrestrained corporate greed in the US. If you're a gamer who's confused about how an open license could be suddenly revoked, don't let Wizards of the Coast fool you. The truth is that it can't be. But Wizards of the Coast is dangling their license and legal team over the heads of the tabletop gaming community. The obvious and rational response is to walk away. They may not actually be able to revoke the OGL 1.0a. But we, the players and creators of tabletop RPG, can devalue it. We don't need the OGL 1.0a. We have alternatives, and some in development. Keep tabletop gaming open, encourage independent and third-party publishers to use open licenses with text that's not copyright or owned by a single company, and no matter what Wizards of the Coast says, keep sharing your ideas, imagination, homebrew, and adventures with the world.