The suit, filed in Utah state court in Salt Lake City, alleges IBM has shared trade secrets regard Unix with members of the free software community, which Caldera says was done illegally.
Caldera does business under the name SCO Group, and specializes in making sure Unix systems operate with computers using Intel Corp.'s microprocessors.
SCO Group, in the complaint says IBM acquired its Unix license in 1995, and there were strict limitations on what intellectual property could be shared with other parties, as part of that agreement.
IBM's interest in the Linux operating system is to sell hardware, software and services to companies that are utilizing the free, open-source code operating system.
SCO in its legal complaint says IBM has "made concentrated efforts to improperly destroy the economic value of Unix, particularly Unix on Intel, to benefit IBM's new Linux services business."