The 100-day countdown to SCO's revocation of IBM's AIX licence ends Friday midnight, and IBM customers are ready to ask Big Blue for legal protection if it becomes necessary.
If SCO revokes IBM's licence it would mean that users are running the operating system without a licence, although in reality this would have little immediate impact.
But there would be longer term consequences if the courts find against IBM.
Ray Titcombe, chairman of council at the IBM Computer Users' Association in the UK, said that customers are "mindful" of the unfolding events, and would seek protection from IBM if needed.
The UK and European user groups will ask IBM to indemnify them if the licence is revoked, but have not yet approached Big Blue.
"If this rises to full litigation then user groups will look for indemnity which quarantines customers from [action] if they are using AIX. We would push vigorously for that," said Titcombe.
Legal action could take years to resolve, and analysts doubt whether SCO has the stomach for such a fight.
If IBM loses, customers are expected to demand reimbursement should SCO charge them for using software code to which they did not have rights.
George Weiss, vice president and research director at Gartner, commented: "IBM has deep pockets and can fight this all the way, or it could opt for a settlement.
"Friday 13 June will be a major turning point in seeing how both companies will move forward."
Gary Barnett, principal consultant at Ovum, added: "SCO can jump up and down as much as it likes but it will have to go to court to get some kind of injunction.
"Nothing has happened in the past week to change the situation. I don't see it as anything more than an irritation that will go away."
But a decision to take legal action stopping IBM from making further AIX sales would leave users in limbo.
"Even if IBM manages to get an injunction to block any potential SCO action, until it is settled there will be uncertainty hanging over future procurement of AIX," warned Weiss.
SCO would not comment on tomorrow's deadline, but last week Darl McBride (pictured), SCO president and chief executive, declared that he hoped the issue could be resolved.
"If we reach the night of 13 June and no resolution has been found we will finalise our decision at that time," he said.
IBM was contacted but did not want to comment.
Article by Rob Jones and Peter Williams. Additional reporting by Jonathan Collins in New York
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