Okay, nothing so far really explains what the OGL is properly. It’s not about what you can do in your personal games with friends; WotC never could and never will be able to control that.

The Open Gaming License is a license that Wizards of the Coast, publishers of D&D, released twenty years ago. It basically made most of the core rules of the game free to use, especially for third party publishers, under certain relatively permissive conditions. This means that other publishers could sell rule books compatible with D&D, using the D&D rules, and WotC promised they wouldn’t sue or demand royalties or anything.

This was not a purely altruistic move by any means. By releasing the rules for free and allowing other publishers to release their own supplements, D&D became THE tabletop RPG, the game that everyone was playing and wanted to play, and WotC enjoyed enormous success from this ecosystem.

It’s also worth noting that game rules are probably not copyrightable to begin with; the exact language used in the books is copyrightable, but systems and equations are not. The OGL lets you use the exact language of the original rules, and was a sign of good faith for WotC that they wouldn’t sue, but people already had the right to make supplements compatible with the D&D rules.

About a month ago, with a new edition of the game on the horizon, WotC tried to release a new version of the OGL with some notable changes. They wanted royalties for publishers making more than a certain amount, they wanted to be able to deny you the right to use the game rules for anything they deemed inappropriate, they wanted to nullify the previous OGL which was supposed to be irrevocable, and… the community reacted. Hard. This OGL update threatened to shut down or heavily hurt tons of smaller publishers putting out RPG content.

They just walked back their stance massively today, after weeks of digging themselves deeper, but it’s been a huge blow to trust that won’t likely recover soon.