Troubled software maker SCO's chief executive has claimed the Linux operating system includes Unix source code, during a court case in which Novell is suing SCO for royalties on Unix.

In the hearing, which concludes on Friday, SCO chief executive Darl McBride made claims — including that "Linux is a copy of Unix" — which are directly contradicted by the open source community and apparently run counter to other SCO testimony, according to trial watchers, including Ars Technica.

SCO sued IBM in 2003, claiming that the IT giant had used copyright code from the Unix operating system which SCO sold, and later extended this suit to other Linux vendors. However, last August, judge Dale Kimball ruled that Novell, not SCO, owns Unix. A four-day court case is now determining Novell's claim for up to US$20 million (AU$21.5 million) in royalties from SCO, which declared Chapter 11 bankruptcy last year.

This court case could be the end of the line for SCO, though some online commentators have suggested the company will find yet another legal avenue of appeal. More interestingly, some observers have predicted that victory for Novell would open the door for it to sue other vendors, including Sun: "I am still going through the Novell financial filings but they could have a claim to a lot more than the value of the SCOsource licences from Sun alone," said one commentator on Groklaw.

SCOsource is a SCO business division that manages its intellectual property around the Unix operating system.