SCO was founded in 1979 by Doug and Larry Michels as a UNIX porting and consulting company. In 1983 they shipped XENIX for the Intel processor, their first packaged UNIX System. Xenix, renamed SCO UNIX in 1989 following SCO's port to the Intel 80386 processor chip, became the most installed flavor of UNIX due to the popularity of the x86 architecture. The company went public in 1993 on the Nasdaq Stock Exchange. In 1995 it acquired the AT&T UNIX source from Novell and the UnixWare operating system, at which time it renamed SCO UNIX as OpenServer.
SCO announced on August 2, 2001 that they would sell their Server Software and Services Divisions, as well as UnixWare and OpenServer technologies, to Caldera Systems, Inc. The purchase was completed in May 2001, and Caldera changed its name to "Caldera International" in May 2001. The remaining part of SCO, the Tarantella Division, changed its name to Tarantella, Inc.
People in the tech community have often not understood why SCO was successful, or why Caldera wanted to buy the UNIX products. This was due to 15,000 value added resellers around the world who provided solutions for customers. For example a doctor's office may want a computer, some terminals, accounting and health management software. The value-added resellers would provide that. The cost of the operating system was negligible, and the VARs liked it quite high anyway since they would add a standard markup to each item sold (5% of $1500 is a lot more than 5% of $29.99). Caldera wanted SCO's VAR channel to push Linux through, banking on larger revenues. In the end, the once loyal channel realised they could do Linux directly themselves and didn't need to be tied to a corporate. Caldera renamed themselves back to SCO since the SCO UNIX products were still doing well mainly due to the huge installed base dating back to the 1990's.
Note: In August 2002, Caldera International changed its name to "SCO Group" to reemphasize its SCO Unix heritage. It is this SCO Group, and not Tarantella or the former Santa Cruz Operation, that started suing IBM in 2003 for $1 billion for allegedly "devaluing" Unix by contributing to the Unix-like Linux operating system. See the article SCO v. IBM Linux lawsuit for more details on that lawsuit.