SCO will start invoicing Linux users in the next two months, with the first batch of bills being sent to around 1,000 US users.

Failure to pay under the highly controversial UnixWare licensing scheme, which was introduced for Linux users in July, is likely to result in legal action, the company warned.

Blake Stowell, director of public relations at SCO, told vnunet.com: "A large number of commercial Linux users could begin receiving [invoices] in the next month or two.

"I would say that a batch in the neighbourhood of 1,000 or so would go out."

Companies based in the UK and Europe will not be in the first wave, with SCO concentrating on US corporates.

But Stowell added: "Sooner or later the invoicing will reach European companies I'm sure. We will not be limiting this to a US only market."

Stowell estimated that there are some 2.5 million servers running a version of Linux based on the 2.4 kernel, the owners of which could receive an invoice.

SCO claims these users require a licence because there is SCO-owned Unix code in the Linux kernel.

"Companies that refuse to pay the invoice may need to have this resolved through the courts, which we're very willing to do. But our hope is that we never have to take that step," said Stowell.

"SCO has to protect its copyrights and, if we have to use the courts to enforce those, we certainly will."

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