Open Source is a term coined by the OSI.
No, it's not:
http://www.catb.org/~esr/open-source.html
And even if it was, popular terms reach beyond the persons/organizations that coined them.
Unless it's trademarked, it's just a term all kinds of people use, many of which don't know/care about OSI.
In fact:
https://opensource.org/pressreleases/certified-open-source.p...
But it was done coincidentally with the discussions that ultimately led to the OSI and the OSD.
>> Bruce Perens has applied to register "open source" as a trademark and hold it through Software in the Public Interest. The trademark conditions will be known as the ``Open Source Definition'', essentially the same as the Debian Free Software Guidelines.
Your own reference contains this text, btw.
I think that basically puts to rest the question of who "owns" Open Source.
OSI has "OSI Certified" as a registered trademark (a certification mark).
No it's not. It's some random group of people that usurped the term and tried to take control of the marketing of a larger movement that was already underway and would have happened with or without them.