IBM customers believe SCO's $3bn lawsuit against the company will fail and have adopted a wait-and-see approach as they continue running the AIX operating system.

The revocation of IBM's AIX licence has left customers in limbo and open to potential future action for running unlicensed software. SCO has filed a permanent injunction requiring IBM to "cease and desist all use and distribution of AIX", and to return all copies of Unix source.

The UK IBM Computer Users' Association (CUA) is holding an emergency council meeting next week to formalise their plan of action. They will lobby IBM to indemnify them against any possible action that SCO might launch against customers running AIX, to protect them against any losses they may incur.

Ray Titcombe, chairman of the IBM CUA said: "This is very, very concerning. We will lobby IBM to issue an insurance statement guaranteeing customers that they will not be in any worse position as a result of this action."

Assurance company Standard Life runs AIX to support a variety of different systems including email, database management and firewalls.

Bill O'Day, director of information systems operational services at Standard Life, said he was tracking the issue and considering the options, such as moving to Linux and other Unix offerings.

But he would only pursue these "if IBM said it could no longer support its service warrant", he said.

"We are looking at our general exposure and if any threats become a reality, but we are playing 'wait and see' and not going for a knee-jerk reaction AIX exit strategy."

Despite revoking the licence, David Roberts, chair of the Infrastructure Forum, doubted SCO would succeed in its claim.

He advised AIX customers to check their licensing and support agreements and to take advice from their supplier. "If SCO and IBM have a ding-dong, it doesn't matter how long it is or how drawn out as long as customers can continue doing business," he said.

Gary Barnett, principle consultant at analyst Ovum, commented: "Should AIX customers be concerned? No. SCO cannot simply retreat. It's a game of chicken, but one is a turkey."

SCO has refused to rule out "enforcing" its rights against AIX customers, but an IBM spokeswoman said the company would continue to defend AIX and its position.

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Additional reporting by Jonathan Collins, Peter Williams and Rob Jones