Linux users are refusing to bow to continued pressure from SCO to buy a UnixWare licence, despite its unpopular decision to bill 1,000 companies in the next two months.

SCO says it will begin legal action against those that do not pay, but most industry watchers think it unlikely the company will carry through its threat. They believe users will largely ignore SCO's claims completely, or at least wait until the IBM dispute is settled.

It is already locked in a legal battle with IBM, demanding $3bn in damages after accusing Big Blue of misappropriating its Unix technology to build up its Linux services business.

"I find it hard to believe that small companies will even bother to respond, and SCO does not have the resources to go after them in a sensible way," James Youngman, treasurer of the UK Unix User Group, told vnunet.com.

"It is likely that SCO will collect money from big companies, but they will pay more out of caution than any conviction that SCO is right."

But Mike Davis, a senior researcher at analyst Butler Group, believes that even larger companies will keep the corporate chequebook safely in the company secretary's drawer for the time being.

"I think that companies will take the invoice and put it on a shelf or deposit it with their lawyers and tell them to wait until the IBM case is settled," he said.

"The IBM case has to take precedence [over any case against users brought by SCO]. What would a company director be doing paying an invoice before a court case is settled?"

SCO, meanwhile, is remaining tight-lipped on how many companies have signed up for a licence, likened by some to the medieval practice of selling indulgences, persuading people to part with cash to buy redemption for their 'sins'.

"We're not giving specific details on [licences sold] just yet," said Blake Stowell, director of public relations at SCO.

"But I can tell you that we had more than 900 calls during the first week regarding the licence, and at least 300 of those were calls from companies serious about purchasing a licence."

Stowell added that the companies invoiced were among the "1,500 largest companies in the world, and also other companies that aren't in that group, but are known users of Linux".