Going forward, if OGL 1.1 is released, and looks like the io9 leaked document, I expect that some beloved OSR projects are simply going to be left as is, and no one will make further compatible material under their license, because their license requires inclusion of OGL 1.0a. Others will do a re-write to distance themselves a bit more from old D&D and put forward a new edition that is not under any version of the OGL, is released as a Creative Commons project, or with their own open license. After all, the OGL was always a voluntary inclusion.
As is, I thought it might be helpful to point out several TTRPGs that are derived from Dungeons & Dragons and retain enough D&DNA that you could use them to play Keep on the Borderlands or Village of Hommlet... But have made substantial enough changes that they risk nothing by ditching the OGL, and have either a generous third part license, or are within the Creative Commons:
- Index Card RPG (Core 2e and Master Edition) by Hankerin Ferinale have some of resemblance to D&D5e and to AD&D, but ICRPG is a very different, very fast, very fun game. It has a very generous 3rd party license.
- Knave by Ben Milton is a very light and fast classless OSR game where gear determines character capabilities, and where magic is rarely a weapon. It has many derivatives such as Brave and Grave. Knave is Under a Creative Commons License.
- Into the Odd is the first of many games built on Chris McDowell's open culture game engine Mark of the Odd. MotO-based games like Electric Bastionland, Silent Titans, Mausritter, Super Blood Harvest,and Death is the New Pink are incredibly fast and demand clever and creative play. MotO is under a Creative Commons License.
- Cairn is the lovechild of Knave and MotO and is definitely greater than the sum of its parts. My own Sci-fi hack of it, Wreck adds in a system for leveling up and underwater adventuring. It's a fully open Creative Commons license.
- Crimson Dragonslayer D20 is the engine running under Cha'alt. The 2022 version is free for download on Drive-thru RPG. While I have not seen any official license of any kind for CDSD20, the creator rends to run a lot of jams and seems very open to saying "go to town" about making material for his work.
- Mörk Borg the apocalyptic Swedish Death Metal game from Fria Lagan is very close to B/X, but is not under the OGL. They have a very generous open license of their own.
- And, of course, my own Deathtrap Lite is also under a Creative Commons license, and have very different rules structure to D&D but using similar enough rules to make a module runnable with only one point of conversion per encounter.
- Edit: Kevin Crawford's Stars Without Number and Worlds Without Number, both B/X based space opera games with a very rich setting and interesting skill system that are released under a Creative Commons License.
I anticipate that, whether OGL 1.1 drops or not, we will see the OGL disappearing from more OSR products, including some of the existing ones in new editions in order to allow the community to keep producing.
Edit: Just as I was putting the finishing touches on this document, I saw that Chris Connerman had, in fact, said that he would do exactly this on the Basic Fantasy RPG forum, So consider them to soon be added to the list.