Update February 8th 2023
Over the course of January 2023 Wizards of the Coast prepared to attempt to deauthorize v1.0a of the Open Game License, then reversed course and took no action. It also released the System Reference Document for the current version of Dungeons & Dragons, known as "5.1" using both the v1.0a of the Open Game License and the CC-BY license from Creative Commons.
At this time we evaluate the current condition of the licensing of the game system as stable and safe. Due in large part to pressure from the community the ultimate resolution of this matter was in our view, favorable.
We'll continue to monitor the situation as it evolves.
Thank you for your continued support for the philosophy of Open Gaming!