There was, of course, a significant effort applied to ensure that Opus was free of these (and other) encumbrances. And the non-RF filings were not updated against future versions of the draft (but they aren't required to be so take that for whatever its worth).
My understanding from the communication we had from QC them was that their disclosure was purely driven by a employee viewing 100k foot level slides at IETF 77, and that they've never conducted any legal _or_ technical review whatsoever, never read the draft, and never looked at the code. They've filed IPR statements against a collection of other similar things, including SIP, Especially after the disclosure a lot of focus was applied by other people to make sure things were clear, something you can't say for SIP (QC's disclosure came many years after the standard was published).
(And now is when I eagerly await your posts on every comment thread about OSS SIP implementations on the net asking them the same thing)
It seems many companies have taken a conservative approach to the IETF IPR policies, with the concern that the IETF rules would be found by a court to bar enforcement of their patents unless they had filed a disclosure, so they broadcast file against anything that touches a space they have a commercial interest in.
Arguably this is a flaw in the IETF process... but when understood for what it is it can actually be quite helpful. If courts do eventually conclude that the disclosures are limiting, even if of just some parities, then even these promiscuous disclosures will greatly aid efforts to write royalty-free standards since they help focus on what review and clearance.
And, of course, if these parties to attempt patent extortion they'll lose their patent licenses to practice Opus from the actual authors. This is something that could be quite commercially expensive. I think the situation is pretty good, or otherwise I would have made sure that the standard was not published. IIRC, the only comments raised during the final consensus comment about the non-RF filings were people saying they were inapplicable.
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