Everyone owns it. No one controls it.

If Hollywood ever made a movie about software, even the most gifted scriptwriter wouldn't dream up the real-world battle now taking place behind your computer screen.

It involves the world's richest man, a band of idealistic computer programmers led by a former Finnish college student, and crazy ideas about software freedom and democracy that threaten the rich man's empire. If it succeeds, the movement would change the way future software gets written. It could also give computer users better programs, cheaper pricing, and a lot more choice over what runs inside their machines.

Those remain big "ifs." But they've become much more feasible in the last six months.

"What we're really talking about is a brand new model, which is changing all the rules," says Paul McNamara, vice president of business development for Red Hat Software, a leading distributor of the new kind of software, based in Durham, N.C.

"What happens is going to have great impact on the software industry itself," adds Ed Taylor, president and founder of Collective Technologies, a systems management consulting firm based in Austin, Texas. "If this becomes successful, then everyone will go to this open-source model."

The revolutionary idea is called open-source software. And it works in ways diametrically opposed to the current way companies make software. Today's computer kingpins, such as billionaire Bill Gates of Microsoft, sell programs but jealously protect the source code that underlies those programs. Microsoft controls when new versions come out and when bugs get fixed.

Under the new paradigm, programmers give away their source code in the hope fellow programmers will change it and release new improved versions. Then, others improve upon those improvements and so on in a virtuous circle. Fundamentally, the battle shaping up between Microsoft and the open-source movement boils down to which model creates the best programs: a software democracy or a software dictatorship.

"The marketplace as it's set up now will only flourish under an operating system dictatorship," says Diganta Majumder, chief technology editor for Windows Magazine. "The fact that Microsoft in effect dominates the operating system market is what has allowed corporate America to buy thousands of applications across the board. [Thus] the very thing that people hate about Microsoft is precisely what gives it stability in the marketplace."

Challenging the Microsoft model

Several open-source programs that go by names such as Apache and Perl are challenging that model. The most famous of them, called Linux (pronounced LIN-ucks), is serving as the test case for whether open-source models can thrive in the corporate world.

Already, it's showing up in unexpected places, such as the space shuttle, the Canadian National Railway, and several major corporations. "Inside any large commercial organization ... you don't have to look very far to find people who like the code and are very sympathetic to the development of something that will challenge Microsoft," says Maureen Dorney, an Internet technology specialist with the law firm Gray Cary Ware & Freidenrich in Palo Alto, Calif.

It's also making inroads in local government. For example, every time a resident of Garden Grove, Calif., signs up for a park recreation class, pays a parking ticket, or gets a business permit, the city's Linux-based computer system handles the transaction. While Garden Grove still uses Microsoft Windows on its desktop computers, the city's information-systems manager, Robert Shingledecker, wants to switch those over, too, as soon as Linux-based office software hits the market.

Mr. Shingledecker may not have long to wait. Many software companies, including big names such as Corel, Netscape, and Oracle, are beginning to rewrite their programs so they'll run on Linux. Well-known computer vendors, such as Dell Computer and IBM, are also lining up behind the open-source movement.

"We want to be a leader in the Linux space," says Jon Prial, director of integrated solutions and Linux marketing for IBM, based in Armonk, N.Y. "It's important to our customers."

Linux is closely watched because it's an operating system, the most strategic type of software (see box below). Microsoft built its dominance with its own operating software called Windows and Windows NT. And while Linux and Windows currently occupy different niches of the market, many observers say they'll soon bump into each other.

Already last year, they were the two fastest growing operating systems around (Linux grew a stunning 212.5 percent), according to preliminary figures from International Data Corporation. The Framingham, Mass., research firm forecasts Linux's growth will outpace that of all other operating systems through 2003.

That's dramatic success for a program written eight years ago by a University of Helsinki student, Linus Torvalds. He wrote it for his own use because he couldn't afford $5,000 for a proprietary operating system known as Unix. "I decided: Yeah, how hard could this be?" he recalls.

When he finished, he posted Linux on the Internet so other students could use it. "I just expected a few comments," he says. Instead, he was deluged by responses from people attracted to its robust performance and eager for an alternative to Microsoft. So Mr. Torvalds handed out the source code without charge but one stipulation. If people made changes, they had to make their source code available, too.

Soon students and other interested developers were flocking to the software and making improvements. As those students got corporate jobs, they brought Linux with them. "They came in and basically had a preference to run Linux on their own desktops," recalls Mike Prince, chief information officer of Burlington Coat Factory Warehouse Corp. based in Burlington, N.J. Then other software developers in the company started using it. Now, the company plans to install Linux machines in each of its 256 stores.

Software by committee

In all, the Linux community counts some 120,000 programmers who use the software and share their advances. Sometimes, teams of programmers compete to solve challenges.

Software committees, made up of certain figures that have gained stature within the Linux community, keep watch over the chaos. The committees decide what changes get made and how they'll be harmonized with the rest of the code. Torvalds still serves on the committee that controls changes on the core part of the software. But at this point, he concedes, at least 95 percent of this code has been written by someone other than himself.

Distributors also have sprung up - notably Red Hat Software in the US and SuSe in Europe - bundling the best parts of the software and selling it at small cost to companies that want to use the program but not piece the free parts together themselves. With thousands of users trying out improvements and getting them tested by thousands of others, everybody gains, proponents say.

"There tends to be a mechanism that only the best code gets adopted," says Mr. McNamara of Red Hat. "I fundamentally believe that this is the model that will set the pattern for software development for the next 10, 15 years."

Open-source software has made enough of a splash that much bigger companies are also toying with the model. Netscape and Apple Computer have released the source code to some of their software. Even Microsoft is making rumblings about it. "We are looking at that and trying to understand what the customer needs are," says Jim Ewel, Microsoft's marketing director for Windows 2000 Server, the next version of Windows NT. So far, though, the company has no plans to release source code or rewrite any of its programs to run on Linux.

Despite its progress, Linux skeptics abound. While the program can run certain back-office functions such as Internet mail, it hasn't proved it can meet a corporation's entire computer needs, Mr. Ewel points out. And it's not even clear that the open-source model will work in the long run. "As soon as you get people involved who want to make money, it becomes less open," says Larry Genovesi, who heads Network Engines, a Randolph, Mass., maker of Linux servers. At some point, developers will look around at their well-paid counterparts in the corporate world and say, "Why am I doing this for free?' "

Linux distributors may become more proprietary as big money moves in. Already, Red Hat has gotten investments from the likes of IBM and Dell. "Now that they've got investors and shareholders, they've got to start acting like a profitable entity," says Mr. Taylor of Collective Technologies. "They very much care that you buy their Linux instead of someone else's Linux." This scenario unfolded for Linux's precursor, Unix. An AT&T creation originally distributed freely among universities, Unix eventually split as big companies developed their own proprietary versions. Will Linux avoid such a split?

It's in the licensing

Open-source proponents say they can. Linux enjoys some protections Unix never had, they point out, including licensing restrictions that make it impossible to distribute proprietary code.

The Linux community is so committed to open sourcing it would shun anyone who tried to go the proprietary route, they add. And while young developers may not get paid to work on Linux, they will get noticed for corporate jobs down the road, says McNamara. "You're becoming a marquee programmer in the industry, and that will have value."

Many observers are keeping an open mind about Linux's potential. "It really depends on whether people can reconcile the open-software movement with commercialization," says Ms. Dorney of Gray Cary Ware & Freidenrich. "I think a healthy dose of skepticism is called for, but I wouldn't write these people off."

Even Torvalds thinks both software models, open-source and proprietary, will coexist for some time.

"What I'd like to see is that in a few years ... when someone goes in to buy a new computer, they can decide [what operating system they want]," he says. "It wouldn't be a default to Windows. If that happens, I'll be happy."