IBM has escalated its legal counterattack on The SCO Group, filing new claims on Thursday in the U.S. District Court in Utah alleging that SCO has infringed IBM's copyright.IBM and SCO have been disputing each other's intellectual property claims surrounding the Linux and Unix operating systems since March, when the Lindon, Utah, company sued IBM, claiming that Big Blue's contributions to the Linux operating system violated IBM's Unix contract.In August, IBM filed a counter lawsuit against SCO, maintaining that SCO had violated not only the GNU General Public License (GPL) software license that governs Linux, but also a number of IBM software patents. The counter lawsuit asserted that SCO's rights to distributed Linux had been terminated. On Thursday, IBM amended its counter lawsuit, adding the charge of copyright infringement, according to an e-mail sent out to the IBM sales force on Friday and provided to the media by IBM.The amendment also asks the court to rule on whether SCO has the right to seek a $699 per processor licensing fee it is now demanding of Linux users. "SCO has no right to assert ... proprietary rights over programs that SCO distributed under the GPL," the court filing says."One of the new counterclaims is that SCO infringed IBM's copyrights by, among other things, copying and distributing IBM contributions to Linux without permission after SCO's rights under the General Public License were terminated due to their breach," wrote Bob Samson, IBM's vice president of systems sales in the e-mail.SCO has not sold the SCO Linux software in question since May 12, but the company continues to distribute it via the Internet to honor existing support contracts, said SCO spokesman Blake Stowell.Stowell disputed the idea that SCO could no longer distribute Linux. "We're the copyright holder for the core Unix operating system. If we want to charge someone a licensing fee for using our copyrighted software that's gone into Linux, then we have that prerogative," he said. "If we want to continue to distribute Linux to our existing customers, we can do that because we own the copyrights on that Unix software."Samson's letter also criticized HP's recently announced plan to offer indemnification to its Linux customers. Indemnification in legal terms means that one party makes good on a loss, or gives security against a loss, suffered because of the actions or default of another party."The typical approach to indemnity, and apparently HP's approach as outlined in the press, we believe runs fundamentally counter to the Linux value proposition," Samson wrote. Because HP's indemnification is rendered void as soon as customers make modifications to the source code, "it will inhibit customers from taking full advantage of the open source development process," he wrote.HP disputed Samson's claim, saying that its indemnification policy would benefit "the vast majority of HP's customer base," who do not make code modifications and adding that the company is willing to consider the possibility of indemnifying modified code on "a case-by-case basis," according to a company spokesman."IBM seems to be trying to drive a wedge where one does not exist," the spokesman said, "HP cannot provide a blanket indemnification for every Linux user."IBM declined to comment.