Currently Microsoft is feeling the full impact of the global economic slowdown. Reduced demand for its Windows OS & other software products has had a negative impact on Microsoft. Both sales & profit are down. Meanwhile, Linux isn't feeling any impact at all.

Linux revenue continues to increase & is right on track of making the open-source OS a $1 billion a year business, according to IDC.

Market analyst IDC estimates that between 2008 and 2013, Linux revenue will deliver a compound annual growth rate of about 17%.

IDC forecasts that Linux revenue will pass the $1 billion mark in 2012 & in just a single year it will grow by an additional $200 million, reaching $1.2 billion in about 3 to 4 years from now.

"The dynamics we are seeing here are fascinating. The convergence of the difficult economic conditions, the maturing of enterprise virtualization software, and the increasing use of replica copy deployments of Linux server operating systems is leading to a shift where the success of the market is increasingly defined by the installed base rather than by the number of brand new subscriptions or deployments being made," said Al Gillen, program vice president, System Software at IDC. "This phenomenon is not unique to Linux – as we see the same trend playing out with Windows server operating environments."

Additional key findings from the IDC study include:

• The top revenue-producing vendors are Red Hat and Novell, which together account for 94.5% of worldwide Linux operating systems revenue in 2008.

• In terms of new subscriptions of server operating environments, Red Hat and Novell accounted for 90% of worldwide Linux subscriptions in 2008.

• Nonpaid Linux server operating systems continues to increase in importance on the overall market dynamics, with nonpaid Linux server operating system deployments accounting for 43.3% of the worldwide total, up from 41.4% in 2007.