Linux sales lost some ground to Windows last year, but are expected to climb in coming years as distributors of the alternative operating system create new revenue streams. According to market research firm IDC, Linux sales declined nearly 5 percent in 2001 to $80 million, but are expected to grow to a $280 million market in 2006. Meanwhile, Windows sales climbed 11 percent to more than $10 billion last year, according to IDC analyst Al Gillen.

"The Linux operating system market, from a revenue perspective, accounts for one half of 1 percent of the total operating system revenue each year, or roughly two days' worth of Microsoft's operating system revenue," Gillen said. "On the second day of January, Microsoft had generated more operating system revenue than the Linux community (will for the entire year)." IDC based its projection of $280 million in sales within four years on efforts by Red Hat, SuSE and others to wring more money from Linux, in part by making it more difficult for users to obtain the software for free, Gillen said. "What we're expecting the revenue to come from is the fact that the Linux vendors are moving toward a model where they're trying to drive revenue per server," Gillen said.