Red Hat and Novell will soon face more competition from a small rival, Ubuntu Linux, in the market for open-source software programs that run server computers.

Mark Shuttleworth, founder of Ubuntu Linux, said on Wednesday that Sun Microsystems would soon certify that his software is compatible with some Sun products.

Sun is the first of the world's major server computer makers to certify that its hardware works with Ubuntu Linux, Shuttleworth said in an interview.

Such certifications are important because there are dozens of types of independently developed Linux software and many of them are not compatible with hardware and software sold by the world's largest computer and software makers.

Red Hat, which reported $523 million in revenue in its fiscal year ended February 29, became the world's largest commercial provider of Linux software for server computers primarily by through such certifications.

Red Hat Linux software is certified to work with hundreds of different software programs and pieces of hardware, a key selling point because it means that customers don't need to spend time customizing the software to work with their existing computer systems.

Terri Molini, a spokeswoman for Sun, confirmed the relationship with Ubuntu, saying she expects the certification will happen "very soon."

Molini said that her company is also working to make sure its Java programming language, tools and Java server are compatible with a new version of Ubuntu -- Ubuntu 8.04 -- that is coming out later this month and code-named Hardy Heron.

Shuttleworth develops Ubuntu with help from software programmers around the world, many of whom contribute their time at no charge. He makes money by selling contracts to upgrade the software, provide help desk support and bug fixes through Canonical Ltd, a privately held company that he owns.

Red Hat and Novell both sell subscription versions of Linux, which come with similar support. 

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