This is the first build of Longhorn compiled after the development reset. Basically, it is Windows Server 2003 SP1 rebranded. There is no evidence that this is a "Longhorn" build except for references in the End-User License Agreement. It was described by Grabberslasher on his UX.Unleaked blog on May 2, 2008.
This build is not functionally a Longhorn build, but since it has the Longhorn EULA (End User License Agreement), it was still distributed as a Longhorn build, and was intended to be tested as such.
Microsoft has having numerous problems with the earlier Longhorn builds, including stability issues, memory leaks, and so on, and because of this, they decided to replace the current version of the underlying Windows Server 2003 codebase with a later version (Windows Server 2003 Service Pack 1, rather than Windows .NET Server 2003 Release Candidate). This build was forked from the same build of Windows Server 2003 Service Pack 1, and still retained certain charactoristics from it, such as the Windows Server 2003 beta-related notice window that would appear upon logging on.Download Link: