> I wonder if the community has grounds to sue any of these companies who are ditching the AGPL in favor of proprietary, source-available licenses, especially under “third-party beneficiary contract” legal theories, like @conservancy did in their suit against Vizio.
> If the source code originally used AGPL, isn’t it still contractually obligated to ensure those rights to its users, including any new source code added to it?
seems to indicate rather strongly that the original poster doesn't understand the AGPL terms, CLAs, or the nuances of contract litigation. At least OP recognises that at least enough to ask a question about it, but I don't think "random questions I thought up about reasonably well-settled law in Twitter thread form" makes a good post.
The OP may not understand why but it is very common to have gaps when relicensing because collecting CLAs, etc, is often allowed to slip to the minimum for the current license terms.