Microsoft has decided to drop the $99 licensing fee previously required for its Services For Unix software and plans to make a new version of the interoperability product available this week at no cost on its Web site.

Services For Unix is a subsystem of Unix APIs and development and administration tools intended to help businesses migrate Unix or Linux applications to Windows computers or create heterogeneous environments where the operating systems coexist. SFU version 3.5, to be available Thursday, will come with performance improvements and new features that make it better at both of those functions, yet Microsoft officials say the price change represents a strategy shift that's equally important.

"The big news on this release, we think, is that it's free," says Dennis Oldroyd, a director with Microsoft's Windows server group.

Microsoft had developed a reputation among some customers for not doing enough to help them deal with the growing number of mixed computing environments. In a survey last fall by InformationWeek Research, more than half of the 400 business-technology professionals who responded said Windows-Linux interoperability was a problem, and 87% were of the opinion that Microsoft was leaving the interoperability work to others.

"The real driver behind this [pricing] change is this interoperability issue," Oldroyd says. "We want Windows to be the best platform for interoperability."

The three main components of SFU--Unix's Network File System and Network Identity Service and Microsoft's Interix layer of Posix APIs--have all been tuned for better performance, with some commands running 50% faster, Oldroyd says. SFU 3.5 also features first-time support for P-Threads (for Posix-compliant multithreaded applications), a broader set of Posix APIs, and updated utilities and libraries.