The SCO Group may have a hard time making its case that Linux includes illegal source code, according to documents published recently on the Web site.

Earlier this week the site published for the first time a ten-year-old lawsuit settlement agreement that grants developers the right to redistribute much of the Unix source code that SCO claims to own and which may ultimately strengthen IBM's defence in a lawsuit between the two companies.

"The agreement actually gives people rights to redistribute (Unix) software that they were not previously aware of," said Bruce Perens an open source advocate and one of the founders of the Open Source Initiative. "It makes it very clear that some of the Unix software that SCO is currently claiming as their own is distributable by the public as open source."

Though software developers generally understood that source code from one of the major variants of Unix, called the Berkeley Software Distribution (BSD), could be freely redistributed in the Linux operating system, the release of the agreement makes those terms public for the first time.

The agreement, obtained by Groklaw under a Freedom of Information Act request, settled a long-standing dispute over the ownership of the Unix source code, fought in the early 1990s between the University of California and an AT&T subsidiary called Unix Systems Laboratories (USL).