Until he launched his legal campaign last year, hardly anyone had heard of Darl McBride. Today, he's one of the most hated men in the computer software business.

"I believe his unpopularity far exceeds that of Bill Gates, who is No. 2," said software developer Ron Newman after hearing McBride speak at the Harvard Law School on Feb. 2.

"Bill Gates has produced something of value," Newman said of the co-founder of Microsoft Corp., who has been reviled for abusing his company's monopoly on desktop operating systems. But Newman said that McBride "has produced nothing of value."

Microsoft refused to comment on the popularity, or lack of it, of its CEO. But there's no question that McBride, chief executive of Lindon-based SCO Group Inc., is widely despised. He's a favorite target for bitter insults on leading Internet technology sites like Slashdot. He's gotten hateful e-mails and been peppered with nuisance calls after someone published his phone number on the Internet.

And the SCO Group Web site has been targeted by computer vandals four times in the past year. The computer worm Mydoom, which made worldwide headlines, caused infected machines to send billions of data requests to the SCO site, knocking it out of commission.

All because McBride has sued one of the world's largest computer firms — International Business Machines Corp. — and, in the process, threatened to derail the popularity of the free Linux operating system, a major rival to Microsoft Corp.'s Windows software.

According to McBride, IBM has taken software belonging to SCO and illegally contributed it to Linux. If the federal courts decide that he's right, McBride will have done what Microsoft can only dream about. He will have crippled the burgeoning growth of Linux — perhaps permanently.

Yet McBride sees himself as the sort of person the geeks of Slashdot should be rooting for — the head of a small business fighting for justice against a corporate giant. "We were forced into a corner where we had to fight," said McBride.

With 2003 revenues of $79.3 million, SCO Group is a relatively tiny software company, but it controls one of the most valuable properties in the industry — the powerful Unix operating system, one of the most popular operating systems for heavy-duty computing tasks. Most major versions of Unix, including an IBM product called AIX, are based on code invented at AT&T Corp. and now owned and licensed by SCO.

According to McBride, IBM has taken large chunks of AIX and incorporated them into Linux, an operating system developed over the past decade as a no-cost alternative to Unix and Microsoft's Windows. Linux is "open-source" code, meaning that anyone can get the raw source code of the software and make modifications to it.

This openness appeals to avid programmers and has spawned a worldwide community of Linux enthusiasts. Companies like North Carolina-based Red Hat Inc. specialize in selling copies of Linux: The software is free, but customers pay for service and support.

Early versions of Linux were far less capable than Unix, but in the past five years, constant upgrades have made Linux a worthy competitor. Many of these upgrades were made by IBM and contributed at no charge to Linux users worldwide, in keeping with the free-software principles that spawned the Linux movement.

But McBride said IBM's license to use SCO Unix forbids the company from doing this. Claiming that IBM's actions have harmed the market for SCO's "legitimate" Unix and cost the company millions, SCO filed a lawsuit against IBM demanding $3 billion in damages. It has since been amended to $5 billion.

The company is also threatening legal action against companies that use Linux, to force them to pay millions in license fees for using SCO's software. SCO is even suing Waltham, Mass.-based software company Novell Inc., which sold Unix to SCO in 1994, saying that Novell is interfering with SCO's effort to enforce its copyrights on Unix.

The barrage of litigation and threats have enraged Linux advocates, but McBride, 44, says he's just defending what's his from IBM, as it strips the SCO brand from valuable software and mixes it with free Linux code.

In person, McBride is hardly the malevolent villain imagined by Linux boosters. Indeed, during his Harvard visit he chatted amiably with some of his harshest critics. David Wilson, a computer science student at Massachusetts Institute of Technology, said he came away unconvinced, but added: "I definitely understand his position a bit better. . . . I see why SCO is pushing so hard."

McBride believes that when he faces his critics, as he did at Harvard, he can defuse their anger.

"You go out and talk to them, and they tend to get a lot more reasonable," he said.

McBride sees himself as a reasonable man. As a child, he was the one who always sorted out sibling disputes. As a young adult, he served an LDS mission to Japan. Later, while working on a sociology degree at Brigham Young University, he volunteered to help a professor with his new personal computer.

Soon he was hooked on the technology and determined to work in the industry. After earning a management degree from the University of Illinois, he held a variety of computer industry jobs, including an eight-year stint at present-day rival Novell, where he spent three years running that company's Japan operations.

McBride became SCO's chief in 2002, after a stint at the business training company Franklin Covey of Salt Lake City. He arrived at a company whose revenues were dwindling, partly due to competition from ever-more-capable versions of Linux. In addition, McBride was disturbed by a comment from IBM software vice president Steve Mills, who said IBM hoped to replace its SCO-derived AIX software with Linux.

How could Linux, little more than a hobbyist's tool a few years earlier, compare with heavy-duty Unix code? McBride began to suspect that IBM was simply donating portions of its AIX code to the Linux community, to hasten the day when Linux and Unix were functional equals — the day when SCO's business would essentially cease to exist.

So McBride ordered an investigation of the code by SCO engineers and outside experts. He says they've uncovered dozens of examples in which IBM mingled SCO-owned code with Linux. IBM denies the claim, saying that SCO's lawsuit is a desperate bid by a fading software company.

"SCO has engaged in unfair competition by falsely claiming ownership of IBM's intellectual property as well as the intellectual property created by the open-source community," said IBM in a countersuit it filed against SCO last August.

One reason why SCO has attracted so much hostility is that SCO has refused to publicly reveal exactly which pieces of its code have been copied, a position that has many Linux advocates claiming a cover-up. Recent hearings by a U.S. magistrate have sought to clear up how much information SCO and IBM need to provide to each other during the discovery phase of the litigation. There'll be plenty of motions and countermotions in the months ahead. The case won't go to trial until April 2005.

While he waits, McBride has plenty to keep him busy. There's that legal squabble with his former employer, Novell, and the possibility of suits against major Linux users. And there's the day-to-day business of running SCO's Unix licensing operations.

The IBM controversy hasn't harmed SCO's business performance — quite the contrary. The company made a profit of 34 cents a share in fiscal 2003, compared to a $1.93 per share loss in 2002. And its stock price over the past year leaped from just over a dollar to more than $22. SCO Group shares were at $13.39 last week on the Nasdaq stock exchange.

His critics say that SCO has built its recent success on savaging the free-software movement. McBride frankly doesn't care what they think.

"I wasn't brought in to have warm fuzzies with Slashdot," he said. "I was brought in to increase shareholder value."

And so far, love him or hate him, McBride has come through.