They can't negotiate with anyone until near the end of that period without breaching their current contracts. To say they refused it misrepresents the fact that the really can't even discuss it.

In all honesty, I hesitate to believe that the offer was serious. It was made by an owner of an NASL team (who has a vested interest in pro/rel, NTTAWWT) in a situation where he likely knew MLS couldn't even negotiate. To me, it all seems like an effort just to make MLS look bad rather than a serious offer. And it pretty well worked.