"I can definitely say that those files were trivially written by me personally, with no copying from any Unix code ever," he told the New York Times, adding that he had written the "horribly ugly" macros as a young C language programmer in 1991.

SCO has attacked IBM and many of its customers, claiming that SCO software code was incorporated into Linux without its consent, and is trying to get Linux users to buy licences for its use.

In a further escalation of the affair, Novell, which once owned Unix, has issued a statement claiming that it - and not SCO - has always owned the Unix copyright, saying it has obtained copyright registrations from the US Patent and Trademark Office in support of its claim.

The company said in a statement: "Novell believes it owns the copyrights in Unix, and has applied for and received copyright registrations pertaining to Unix consistent with that position."

This week SCO released its full-year financial results, showing fourth-quarter revenues of US$24.3m, including $14m for Unix products and services. For fiscal year 2003, the Company reported net income to common stockholders of $5.3 million, or $0.34 per diluted common share, reversing a net loss of $24.9 million, or $1.93 per diluted common share, in fiscal 2002. This marks the first time in its operating history that the Company has been profitable on a full-year basis. Additionally, fiscal 2003 revenue rose 23% to $79.3 million from $64.2 million in the previous fiscal year.