Shares in SCO fell by nearly 72 per cent on Monday as shareholders responded to a court ruling stating that the company does not own the copyright to the Unix operating system.

At $0.44, SCO is valued at a mere $9.4m. SCO's value peaked at $400m in 2003, shortly after it kicked off a legal campaign against Linux users and developers, claiming that the open source operating system had illegally used code from Unix.

In a legal claim against IBM, SCO demanded billions of dollars in damages.

SCO briefly offered a licensing programme through which companies could buy indemnification from any legal claims.

The programme produced several million dollars in revenues. Microsoft and Sun Microsystems respectively paid $16.8m and $10m for a licence.

The SCOsource programme was suspended when Novell claimed that it was the legal owner of Unix intellectual property.

A judge ruled in Novell's favour on Friday, eliminating the foundation underneath SCO's claim against IBM.

The ruling also stated that SCO should have paid its Unix licence revenues to Novell.

If upheld, the latter will effectively bankrupt the organisation as it has spent the past licence revenues on its legal case and to cover losses from its dwindling software business.

The plunge in its stock price puts SCO back in delisting territory. The Nasdaq exchange where SCO stock is traded requires that stock prices surpass $1 and will cease trading if a company fails to comply.

SCO had been briefly delisted in 2005 when it missed several filing deadlines for its annual report and averted another delisting earlier this year after its stock price briefly fell below the $1 mark.

SCO said in a statement posted on its website that it was disappointed in the ruling, and vowed to continue litigating where possible.

"Although the district judge ruled in Novell's favour on important issues, the case has not yet been fully vetted by the legal system and we will continue to explore our options with respect to how we move forward from here," the company said.