Along with the Open-Gaming License, the makers of Dungeons & Dragons have provided another way for people to create content for the game.
The Dungeons Masters Guild hosts material which includes pdf and Print-on-Demand reprints of older Dungeons & Dragons publications stretching back to the origins of the game. It also hosts new material provided by Wizards of the Coast for Dungeons & Dragons 5th Edition.
The Dungeon Masters Guild also allow fans to create their own content for Dungeons & Dragons, that they can upload and sell through the website. They currently allow users to create content for the Forgotten Realms fantasy setting, the Ravenloft horror setting, the Ravnica setting (which is based on the Magic the Gathering card game) and the Eberron fantasy/steampunk setting (along with generic content).
This also allows the use of material not permitted by the Open-Gaming License.
Wizards of the Coast actively encourages their fans to create. They provide artwork which can be used by creators and they run the Guild Adept program for promising game designers, which brings creators together to create official content which is released through the DMs Guild.
It is truly noteworthy how Wizards of the Coast have encouraged creativity and actively seek out new talent.
You can find the Dungeon Masters Guild here; https://www.dmsguild.com/
And you can find the Content Guidelines here; https://support.dmsguild.com/hc/en-us/articles/217028818-Content-Guidelines
If you’re a writer, and you have any interest in roleplaying games, I strongly encourage you to check the website out.