I may not have any pull here, but based on my reading of this entire thread, my opinion is that yes, EskimoBob sold his silence and has broken the contract, but a contract like this should have been offered and probably can't be enforced. 

It is legal (though probably not constitutional) in the USA to pay off for silence (and it's done all of the time), but the contracts to do so are much more detailed and specific than the simple condition expressed in the forum.  If you really wanted to buy his silence, you should have drafted a real contract and NDA, properly negotiated the terms, signed and notarized.

If you really wanted to stick it to him, you could file in small claims court against him.  The likelihood of him showing up is small and you could probably get a default judgement in your favor without ever having to argue the details of the contract.  But my recommendation, even though you didn't specifically ask it of me... just write it up to a life lesson, refuse his business in the future and move on.