Novell chief executive Ron Hovsepian has fired off a furious open letter in an effort to limit the damage caused by Microsoft CEO Steve Ballmer's comments last week to the effect that all Linux users owe Microsoft money.

Ballmer appeared to confirm the Linux community's worst fears last week when he suggested a recent deal between Microsoft and Novell was just the beginning of a patent licensing program that would eventually be extended to all Linux distributors and users.

In a question-and-answer session after his keynote speech at the Professional Association for SQL Server (PASS) conference in Seattle, Ballmer said Microsoft was motivated to sign the deal with Suse Linux distributor Novell because Linux "uses our intellectual property" and Microsoft wanted to "get the appropriate economic return for our shareholders from our innovation".

Ballmer went on to describe Linux as "an undisclosed balance-sheet liability" and said only Suse Linux users "have paid properly for intellectual property from Microsoft".

Hovsepian in his letter is clearly concerned that Microsoft might use the deal to decimate the Linux economy and hold all Linux users to ransom -- a scenario previously voiced only by the most hard-core conspiracy theorists.

"Since our announcement, some parties have spoken about this patent agreement in a damaging way, and with a perspective that we do not share... We disagree with the recent statements made by Microsoft on the topic of Linux and patents," Hovsepian wrote. "When we entered the patent cooperation agreement with Microsoft, Novell did not agree or admit that Linux or any other Novell offering violates Microsoft patents."

He went on to describe all that Novell has done to protect the open source community from patent litigation, such as using the company's own software patent portfolio as a shield, speaking out against an E.U. directive that would have liberalized software patent practice, offering indemnification to its Linux customers and efforts to reduce the issuance of "bad patents" in the U.S.