Microsoft is set to include its Services for Unix (SFU) add-on for Windows as an integral part of the next major release of the Windows server operating system, codenamed Longhorn and expected in 2008. Some analysts said the move could eventually sideline conventional Linux and Unix operating systems.

A growing number of firms are using SFU, currently a free add-on for Windows 2000, 2003 and XP Professional, because it enables a single system to run Windows, Linux and Unix software.

Systems running SFU provide an excellent environment for integrating applications - for example, to add Active Directory support to a Unix application.

Jason Zions, a solutions architect at Microsoft, said there are development versions of SFU that enable a single process to run code both from Windows and Unix libraries. Currently this feature, which would dramatically ease integration tasks, is not available in SFU. Zions said, "We've been working on research versions that would solve that particular problem. It wouldn't surprise me to see that capability appear in a future release of Windows."

Dan Kusnetzky of analyst firm IDC said SFU was one of Microsoft's hidden jewels. "It's a very powerful capability that Microsoft very seldom speaks about," he said. "Rather than hide this product behind Windows they should lead with it. Many firms might be much more interested in Windows if it worked in the way they are used to doing things."

By including SFU in Windows, Microsoft could rapidly become the biggest supplier of Unix software if Longhorn proves a success, undermining traditional Unix vendors such as Sun, HP and IBM, as well as Linux vendors' enterprise offerings.

Microsoft has already confirmed that Longhorn will include a technology called "server roles" to make it easier for IT staff to build Windows servers suited to a particular task, such as file serving. Experts said SFU could surface as a new server role in Longhorn.

SFU is not shipped with Windows because SFU currently contains open-source software, such as the GNU C compiler, which cannot be distributed with commercial software. Zions confirmed that Microsoft is working to replace all open-source code in SFU with commercially licensed alternatives. Last year it licensed Unix software from SCO.

Microsoft may also release a 64bit version of SFU this year. Zions suggested that Microsoft would soon support 64bit x86 processors such as the AMD Opteron and Intel Xeon EM64T chips, saying, "SFU 3.5 today does not run on Windows 64bit platforms, but when I get home I am putting in an order for a 64bit AMD laptop because I have to demo this stuff."