SCO Group CEO Darl McBride has outlined to Infoconomy the basis of his company's legal action against IBM over the open source operating system Linux — and charged IBM with being the source of the majority of the contentious Linux code.

In the interview, to be published in full next week, he reiterated his belief that code that infringes SCO's Unix intellectual property was contributed to Linux from a variety of sources, not just IBM. However, IBM was nevertheless the source of the "majority" of it and much of that came from IBM's Sequent acquisition, he suggests.

He also criticised the basis of open source software, suggesting that its spread might ultimately undermine the development of the software industry.

McBride said that he initiated an investigation into the provenance of Linux code in January this year after IBM Software Group senior vice president Steve Mills had pledged at LinuxWorld to 'transport' IBM's knowledge of AIX into Linux. "That startled us because they have contracts that state that they won't do things like that," said McBride.

"We investigated further to see if their words were matching their actions and, sure enough, they had been taking a significant amount of Unix technology and putting it into Linux. Then the question was, of those pieces, which ones were derivative works of ours? The answer was that there were a lot of them that were," he said.

Further investigation led SCO executives to believe that it was not just IBM that had infringed SCO's Unix intellectual property.

"What we found was that the infringements went way beyond just IBM's involvement and that other parties had contributed things improperly… in going through the process, we counted over a million lines of code that we allege are infringed in the Linux kernel today out of a total code base of five million," added McBride.

Nevertheless, IBM was the source of most of that allegedly tainted code, said McBride: "The vast majority of that did, in fact, come from IBM and when we say IBM, the majority of that actually came from IBM's acquisition of Sequent."