https://nothings.org/stb/stb_opus.html
This essentially causes opus to never be used in games or in things in stores that may have issues with specific licenses.
The licensing restriction is unfortunate, but only restrictive for those with very specific goals, under normal conditions BSD is a wonderful license for game devs since you’re free to use the code and only have to add an acknowledgement somewhere.
I suppose a public domain game might hit the same limitation, though as a non-lawyer I would guess the chance of anyone with standing trying to sue anyone implementing from this spec is realistically zero (though I don’t fault stb for being unwilling to roll those dice!)
And it's not as though libopus is an outlier in using a BSD license. A lot of other commonly used libraries have similar licenses; a few examples that come to mind which are likely to show up in games are zlib, curl, Lua, and SDL.
https://www.audiokinetic.com/en/community/blog/a-guide-for-c...
The intent of the legal language in that spec is pretty clearly that you have to use the BSD license if you copy that code, but if you merely read it to understand the spec then you don't.
>Clean-room design is usually employed as best practice, but not strictly required by law.
As the article points out, if this was actually true then we could change the licensing on code examples found in RFCs to fix the issue, but there doesn't seem to be any actual issue here. Imagine a world where simply reading some code caused licensing issues...