In the UK enterprise market, Microsoft OSes are the most common choice among the FTSE 100, with 52 member web sites running Windows, while 18 are hosted on Solaris and 16 use Linux.

Numerous analyses have noted that Sun appears to be focused on competitive comparisons with Linux, and especially Red Hat, the most popular Linux distribution in terms of market share with 49 percent of web-facing Linux sites. Seven companies in the Fortune 1,000 have shifted their web sites from Solaris to Linux in the past three months, according to our Web Server Survey, with four of them adopting Red Hat.

Solaris’ web-facing hostnames and active sites have remained relatively steady in our Web Server Survey since mid-2003, with its market share trending slightly lower due to strong hostname growth at dedicated hosting companies and domain registrars, who have tended to favor Windows or Linux.

Sun’s approach to Solaris 9 once led us to comment on Sun’s “relaxed view about evangelising new operating system versions.” However, Sun president and chief operating officer Jonathan Schwartz yesterday called Solaris 10 “the most anticipated product release in the history of Sun.”

“Operating systems matter now more than ever,” said Schwartz. “Solaris 10 is an industry milestone, bar none. This is the result of Sun’s huge investment in R&D and demonstrates how superior engineering can deliver real customer advantage.”

The hoopla arrived ahead of the launch version of the operating system, which is scheduled to be available in January, along with source code. Sun has not yet said precisely what type of free license will be used for Solaris 10.