github.com
Of course not.
Oh yeah, that's a good point. It's fairly likey there are lots of different versions of the same engine, and as the developer, ID can give each of them different licenses.
Technically, it's not different versions as much as it is different licenses. It's id's code, and they can do what they want with it, including licensing it in multiple different ways.
The only accusation libretro made was that they're not releasing the source, and them finding that disappointing. They made no claim that id are using contributions made under GPL or are violating the license. That's OP's interpretation.
Id own the original source code and can do whatever they want with it under whatever license. But they don't own code made by external contributors and committed to the public repo. Those contributions are GPL licensed and even id can't use them without adhering to the license. They definitely have a private repo, but it can't be in sync with the public one (unless they have a license in place that grants them the rights to all contributions, I haven't checked out the details of the licensing on the repo).
Exactly.so, tl;dr
To be fair, the libretro tweet is just talking about how they feel "betrayed" because this release isn't open-source. While it shows unfamiliarity with how id has always approached open-source and comes off as silly entitlement, it's not an actual accusation.
