So can someone help me untangle how this relates to possible Zstandard patents?

Back some time ago, when all public facebook git repositories had a patent "grant" document, there was some angst about what exactly this meant: https://github.com/facebook/zstd/issues/335 -- this was considered "resolved" when facebook decided to distribute the software under GPLv2, though after reading the relevant sections of GPLv2 I can't say I follow why this was supposed to resolve any uncertainty around potential FB patents of zstd.

Under BCP79 it would be Facebook's duty to disclose any IPR it has in zstd; there are presently no such disclosures registered: https://datatracker.ietf.org/ipr/search/?draft=&rfc=8478&sub...

As far as I can tell, this is good news for people who would like to adopt zstd!