As part of its Windows 2008 Server reviewers gathering this week in Redmond, Microsoft outlined how it will deliver the editions of the long-awaited Longhorn server with a few surprises. The company announced Windows Home Server, and a new midrange server edition that falls between Windows 2008 Small Business Server and Windows 2008 Server Enterprise called Essential Systems Server 2008.

The striking part of its Windows 2008 packaging announcement, though, was Microsoft’s admission of a server code fork that could cause headaches for application developers.

The Home Server, released to manufacturing in July (HP will be the first OEM to ship it, imminently) is designed to service the needs of 10 home systems, and not 11. The big deal about this edition is that it acts as shared storage and archiving for Windows (and Macs and others soon) clients. It backs up the machines it serves, and serves as a Web host, easily configured storage center and multimedia gateway device. You can also access it remotely from work or a hotel room, or any mobile vantage point. What Home Server isn't is Windows 2008 Server. No support for running Microsoft Exchange, or other hefty Microsoft server-based applications will be offered (although it might work, wink wink).

You can buy Windows Home Server on Amazon.com dirt cheap – it’s only $199. But it will likely be a sweetheart of OEMs, so you'll see it powering hefty little servers.

And while the Home Server has it basic roots in the Longhorn software, its code also veers from its high-end siblings. Apparently, the Microsoft product group that builds Windows Home Server is powerful enough to cherry-pick, then cobble together, whatever bits they want to build this server system software from Windows 2003 Server editions, Windows Vista and XP editions. Networking, as an example, has to be painfully simple to allow XP and Vista Home editions to join up, as they're otherwise largely bereft of networking intelligence.

This is a significant departure for Microsoft, which for many years at least paid lip service to unifying its code base for the sake of developers’ sanity. It was just with Windows 2000 that Microsoft unified its very dissimilar versions of Windows, Windows-over-DOS (Windows 3X, 9X and ME) and the Win32/Windows NT API set. This union matured with Windows XP and Windows 2003 Server editions. Now, however, we’re back to two code bases. That’s double the application development, double the certification processes. Were this to happen with Linux, a cry would be heard across the planet. Nonetheless, several prominent application developers (Avast and F-Secure antivirus, Sonos and LobsterTunes for media in addition to a raft of home software-focused developers) have already lined up with updated/modified applications for Windows Home Server.