SCO Group has hit back at IBM's latest legal challenge in the row over intellectual property rights and the Linux operating system.

In an amendment filed last week, IBM claimed that SCO violated the GNU General Public Licence (GPL). Based on this violation, IBM now argues that SCO has in turn violated IBM copyrights.

But SCO maintains that this argument will not stand up in court.

SCO claims that it owns core intellectual property within Linux and has launched a lawsuit alleging that IBM allowed SCO's code to be added to Linux.

IBM retaliated by launching a legal complaint against SCO. But SCO attempted to distance itself from IBM's decision to use the GPL as a legal weapon.

"IBM, not SCO, has brought the GPL into the legal controversy between the two companies," SCO said in statement.

"SCO believes that the GPL, created by the Free Software Foundation to supplant current US copyright laws, is a shaky foundation on which to build a legal case.

"By contrast, SCO continues to base its legal claims on well-settled US contract laws and US copyright laws."

According to SCO, the GPL has never faced a full legal test, and SCO is confident that IBM's latest action will not stand up to court scrutiny.

SCO said in a statement: "By so strongly defending the controversial GPL, IBM is also defending a questionable licensing scheme through which it can avoid providing software indemnification for its customers.

"We continue to urge IBM to provide legal indemnification for its Linux customers."

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