Taking a leaf from Linux's book, Sun Microsystems will later today make its newly developed Solaris 10 operating system available for free, charging customers only for support.

The latest version of Solaris is scheduled to be unveiled at an event in San José, California as part of the firm's quarterly roundup of product announcements.

Solaris 10 marks a major effort by Sun to regain some of the ground it lost over the past years to Linux, according to Mark McLain, vice president for software marketing at Sun.

"The movement away from Unix and Solaris has been dramatic. We come out now and say: 'We have an alternative for [Linux].'"

Some of the operating system's key features were designed specifically to appeal to users switching from Linux to Solaris.

Among them is an application codenamed Project Janus that allows users to create a virtual container inside Solaris in which they can run Linux applications. This enables them to use Linux applications that are not supported for Solaris.

DTrace is another feature which McLain claims is getting a lot of positive feedback from users. By measuring the performance of individual applications, DTrace lets the IT department pinpoint bottlenecks in the system and improve overall performance.

McLain likened the diagnostic tool to a physical exam where a physician looks for clogged arteries to improve overall blood flow.

Sun's operating system offering will be most appealing to enterprises that in the past abandoned the Solaris operating system because they switched to cheaper servers which Solaris did not support, according to Gary Hein, vice president and service director for application platform strategies with analyst firm The Burton Group.

"[Solaris 10] should change a lot of people's considerations of running Linux. It's very compelling," he said.

The big question remains as to whether Sun can make enough money from the software by just charging for support, Hein noted, pointing to the meagre revenues of Linux providers like Red Hat and SuSE. "There is money in there, but not hundreds of millions," he warned.

Since Sun is travelling down the road of the Linux business model, some users might be disappointed that the company will not today announce the release of the Solaris source code.

It has previously promised to transfer the code to the public domain, but has not yet disclosed when such a move will be made.

McLain promised that Solaris will be open sourced "around year's end".