Well, considering that the rules have changed and more than one affected merchant has discussed the access as being part of the original agreement, I would suspect that the verbiage has been changed since they signed up or that the document you linked to was not the one they were referring to.

It appears that the Merchant Resource Center document has been revised to include the "If a Renderosity MarketPlace Merchant has a vested interest in a competing broker site or is not participating in a professional manner Renderosity Administration reserves the right to remove their access to the Private Merchant forum." at or about the time the original decision was made.

I am sure the affected merchants would be better poised to answer that question.