Unix veteran Greg Lehey has hit back against claims by SCO that the Linux operating system doesn't even exist, but is merely an unlicensed version of Unix.

Calling the comments by SCO's Australia and New Zealand managing director Kieran O'Shaughnessy "stupid", the former Australian Unix Users' Group president and Unix veteran, gave the benefit of his personal experience over 25 years.

"The claim 'Linux doesn't exist' is so obviously stupid," Lehey said. "I've seen the beginnings of Linux since about 1992 and looked at the code and it looked absolutely nothing like Unix. I actually had access to the Unix source tree at the time." Lehey, a director of storage systems development for a software vendor, believes SCO is changing its tune and becoming "more vague" about what's wrong.

"Last year, when they brought out that stuff in Las Vegas they found that they themselves had released the code for one of them, and the other was generated by a code generator. It's interesting that they made this mistake: according to the BSD licence, the SCO code in question should contain a licence statement. How did they miss it?" he said. "That's the only time they came up with any so-called hard evidence and that was such a flop that they are not going to do that again."

Lehey went on: "At this AUUG conference two years ago, we celebrated Caldera - as SCO was called at the time - as being the good guys of open source because they had just released the old versions of Unix under a BSD license," he said. "And that was less than a year before they decided to go and make these stupid claims."

In response to SCO's other claim of "being a defender of Unix", Lehey asked: "What is Unix any more anyway? Where can you go and buy Unix? You can buy Solaris, you can buy AIX, you can buy Irix. The only Unix you can buy is UnixWare from SCO.

I think everyone has seen as much of SCO's side of the story as they want people to see. What we're really seeing is that they're bluffing. If it wants removal of the stolen code, tell us where it is and we'll remove it."

Lehey likened SCO's litigious action to the Unix wars 10 years ago when AT&T was against the BSD projects "when they actually did find small quantities of code which had obviously grown out of the original AT&T code". But, he says, it was trivial "and it came out immediately, was replaced with something better, and that's what would happen here as well."