I guess I don't keep up on these things like I should. But a buddy from out in Redmond just sent me email to tell me that the Longhorn Server Beta 3 WDK is up and available on Microsoft Connect, and available to anybody who wants to try it out. Seems like it's been there since, oh, 26 April or so.
The good news? This latest Beta WDK is only a svelte 605MB. Slimmed-down considerably from the porky 2.5GB Vista version that included DTM (which has been moved to a separate Windows Logo Kit, see my memo from last month).
Note that you don't have to be a member of any official Microsoft beta program to get the Beta WDK. But, please do remember that it's a Beta.