If the OSI members wanted to "clarify the terminology" in a way that permitted them (and you) to exclude others, trademark law would have absolutely been the correct way to do that. It's too late, however. The ship has sailed.

Come up with a new term and trademark that, and heck, I'll help you out with a legal fund donation when Facebook and friends inevitably try to appropriate it. Apart from that, you've fought the good fight and done what you could. Let it go.