When is Open Source not Open Source?

A recent article in Network World contained some interesting caveat emptors about marketing open source software.  The first part of the article -- discussing whether open source is really free or secure -- is nothing new.  But then, the article mentions this:  "Some software vendors playing fast and loose with the rules have slapped an "open source" label on software that in fact turns out to be a "free to download and use" version of proprietary software that cannot be altered or distributed."

This raises an interesting potential legal issue that has not yet come to fruition.  Key "trademarks" in the open source space such as "open source" and "Linux" are probably largely genericized, so it seems unlikely that claims will arise as to whether inaccurately calling a product these things is a trademark infringement.  However, I have been surprised not to see a fraud or false advertising claim based on a vendor identifying software as "open source" when it is not.   It's unclear what the damages might be if the software is gratis but not libre, but that has never stopped a class action plaintiff's lawyer, as far as I know.