In January, Microsoft released the latest version of its UNIX interoperability tool, Windows Services for UNIX (SFU) 3.5. This version of SFU adds support for Windows Server 2003 (and, consequently, drops support for Windows NT 4.0), extends the Interix execution environment to support more complex applications, and includes a few interesting new features and licensing terms. Here's what you need to know about SFU 3.5.

Why and Where
Microsoft first introduced SFU to answer complaints that it lacked an interoperability strategy in this increasingly cross-platform world, and it wanted to help enterprises move legacy UNIX applications to more easily managed Windows machines. SFU offers a full UNIX execution environment that gives UNIX administrators, developers, and IT pros the tools they want. SFU includes directory and file-system integration, so for example, you can link UNIX logons to Active Directory (AD) logons and perform other basic integration tasks. Also, developers can use SFU to integrate UNIX solutions into COM objects, Web services, Microsoft .NET applications, and other programs.

New Features
Microsoft has significantly enhanced and tuned NFS, Network Information Service (NIS), and the Interix subsystem to perform more quickly. The Interix execution environment now supports the UNIX P-Thread multithreading system, which lets developers port over more complex custom applications than they could in earlier versions. The company has also improved SFU POSIX support. And in addition to the latest version of the X Window System, X11R6.6, SFU 3.5 includes the latest version of many popular UNIX command-line tools.

The best feature of SFU 3.5, however, is its licensing cost—there is none! The product is available for free to users of Windows 2003, Windows XP Professional Edition, Windows 2000 Server, and Win2K Professional. Previous licensing terms required a $99 fee per client or workstation.

Recommendations
SFU 3.5 is an excellent solution for anyone migrating UNIX applications to Windows or trying to interoperate between UNIX and Windows systems. Cynics will note that Microsoft's new pricing strategy was influenced by the free nature of Linux, but who cares? I highly recommend SFU 3.5.