Just speculating here...
As far as I interpreted things (unless the thread linked in this thread is newer), GR was on the fence whether or not they wanted to pony up the $5,000 for an advance copy of the rules as a leap of faith. It is assumed that 4E rules will be good, but (GR realizing that this is an assumption and not a guaranteed event) on the remote chance that they are not then GR does not want to be out the $5,000.
From Chris' post here, sounds like they are getting a peak for free or maybe at a reduced cost with some kind of additional agreement. Just speculating here, "If we like em, we will pony up the $5,000 so we can produce product near the launch. If we don't, we will agree to not produce something for an ADDITIONAL 6 months after everyone else is able to do it." Or maybe Wizards thought, "Hmmm, GR makes good stuff, and helped us sell 3.5 PHBs & DMGs, we will give em a peek for free so GR can make a more informed decision."
Anyways, I hope GR and the Game Mechanics make 4E stuff because they do good work.