Your guide to the past, present and future of the legal challenge that may change the face of the open source revolution.

It began with a simple asset inventory. In June 2002, President and CEO Darl McBride joined SCO, and, looking for ways to turn around his fizzling little Unix/Linux company, it dawned on him that SCO owned something valuable: the Unix System V source code.

At first, SCO planned to use its Unix source code to allow old Unix apps to run on the new Linux operating system. In fact, according to Chris Sontag, SCO senior vice president and general manager of the company's licensing division, SCO even briefed analysts on this strategy.

In the meantime, some Linux users had taken it upon themselves to use SCO's Unix software to run Unix apps on Linux, which was illegal for anyone but SCO to do under its Unix licence. SCO devised a plan to allow these users to do so legally through a new licence.

But before SCO started offering the new licences, IBM took the wind out of SCO's sails. At LinuxWorld in February 2003, IBM senior executive Steve Mills revealed his company's plans to use AIX, IBM's own Unix platform, to accelerate Linux development. "It sounded like they would take all of AIX and put it on Linux, basically obliterating Unix," says Sontag.

SCO was alarmed. Even so, the company continued to dig into the Linux kernel's source code, as it was still thinking about ways to allow Unix and Linux to run together. In February 2003, SCO allegedly found Unix System V code and Unix derivative code in Linux kernel version 2.4.

The implications - to SCO - were clear. If Linux contained SCO's proprietary code, then Linux (which under the General Public License mandated free distribution of the code) was violating SCO's Unix licence. Therefore, SCO could now challenge the legality of the Linux licence, thus radically affecting not only how Linux was developed and sold, but also its viability as a corporate platform. Indeed, everyone using Linux with Unix stuck into it would, in theory, owe SCO a fee. If SCO could prove its case, it was sitting on a gold mine. So SCO left the Linux business and entered the litigation business. Who's Who

In the SCO Corner

SCO President and CEO Darl McBride - The central figure in the maelstrom, McBride tries to focus on SCO's business and products. "In spite of the popular media saying we're the most hated company in technology, customers are fairly pleased with the direction of the company," he told CIO, several months before posing for the cover of Fortune wrapped in a printout of the Unix development history time line.

SCO Senior VP and General Manager of SCO's licensing division Chris Sontag - Bad cop to McBride's good cop. Sontag is focused on extracting licence fees from users that SCO claims are in violation of its licence, and he casts the lawsuits in dramatic terms: "We are not putting a lot of energy into settling. The battle lines are drawn. It's a death match. We either win or die."

Attorney David Boies - Boies accepted $US1 million in cash and 400,000 SCO shares to take on IBM. Ironically, Boies once defended IBM in its 14-year antitrust suit, and he was the US Justice Department's lead prosecutor in the Microsoft antitrust case. Now, his success prosecuting Linux and Unix users like IBM may contribute to the success of the company he wounded (Microsoft) and wound the company he helped save (IBM).