In the latest twist in the unfolding drama that pits SCO Group against Linux distributors--and potentially against Linux users--SCO said Monday that Microsoft has agreed to license its Unix technology.

SCO, which claims ownership of the Unix operating system source code and rights to Unix licenses that go back years, has been ratcheting up efforts to protect its intellectual property. In March, SCO filed a lawsuit against IBM, charging the company with making "concentrated efforts" to destroy the value of Unix-on-Intel to benefit IBM's Linux services business. Last week, SCO issued a general warning that Linux is an unauthorized derivative of Unix and said liability could extend to companies that use Linux. SCO suspended distribution of its own Linux versions, SCO Linux and Caldera OpenLinux.

Microsoft has agreed to license SCO's Unix source code and an unspecified SCO patent. In a written statement, Microsoft indicated the SCO technology would be used in Microsoft products that support Windows-to-Unix interoperability, including its Services for Unix software. The decision to sign a license with SCO "is representative of Microsoft's ongoing commitment to respecting intellectual property and the IT community's healthy exchange of IP through licensing," Microsoft's general counsel, Brad Smith, said in the statement.

SCO Group was formerly Caldera International, a company founded in 1994 (as Caldera Inc.) to compete in the Linux business. In 2001, Caldera acquired the Unix server software and services division of the original SCO; in 2002, Caldera changed its name to the SCO Group.