It’s not a term, it’s a phrase. It means “open source advocates who are being honest about their advocacy”, in case you really need such a degree of clarification.

I’ve met honest open source advocates before and, once again, they would be unlikely to refute the fact that “open source” was invented in explicit contrast to “free software” to achieve corporate palatability.

The comment you are responding to was literally responding to a comment which validated this exact sentiment.

As to providing evidence, those of us who were there at the time don’t need any and those of you who weren’t ought to seek some. It’s not my job to link to the nearly infinite number of conversations where this obvious dynamic played out.