Microsoft Corp. (MSFT) has given the most detailed description to date of the number of open-source computer programs it says infringe on its patents, but the company says it still prefers licensing deals with open-source developers, software distributors and users instead of legal action against them.

"There is no reason why any segment of the industry needs to be exempt from intellectual property rules," Horacio Gutierrez, a Microsoft vice president for intellectual property and licensing, said in an interview Monday.

At the most basic level, open-source software is distributed free of charge to consumers or businesses to use on their computers, and to programmers to modify, build on, and distribute again — also for free.

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While proprietary software companies like Microsoft make money by selling licenses for programs, open-source companies give away the program and usually make money selling support services.

Open-source programs step on 235 Microsoft patents, the company said.

Free Linux software violates 42 patents. Graphical user interfaces, the way menus and windows look on the screen, breach 65. E-mail programs step on 15, and other programs touch 68 other patents, the company said.

The patent figures were first reported by Fortune magazine.

Microsoft also said OpenOffice, an open-source program supported in part by Sun Microsystems Inc. (SUNW), infringes on 45 patents. Sun declined to comment on the allegation.

Microsoft is the dominant maker of software that powers servers and desktop PCs, but the company views the free or low-cost Linux operating system alternatives "with a great deal of concern," said Al Gillen, an analyst at the technology research group IDC.

"It's one of the few operating systems that represents a viable threat that Microsoft has a great deal of difficulty containing," Gillen said, because the developers share their code.

"Microsoft can't drive a company out of business and make Linux go away," the analyst said.

Instead, Microsoft has struck a number of patent-licensing deals with companies that use open source code, most notably Novell Inc. (NOVL) last November.

In one aspect of the deal, Microsoft agreed to sell Novell's flavor of Linux, called SUSE Linux. It also agreed not to sue the customers who bought it, even though it claims the open-source software infringes on its patents.

"Microsoft could have chosen to litigate many years ago, but we have decided not to do that," Gutierrez said.

Instead, in the interest of making sure programs that include open-source technology work well with Microsoft products and vice versa, the company will continue to pursue similar deals.

Much of the open-source community was unhappy with the Novell deal, which it saw as a workaround to a widely used open-source license called the GNU General Public License.

More broadly, the free software movement saw the deal as an attack on one of its core tenets.

Under the public license, once open-source code is incorporated into another company's technology, the new product must also be freely available — a distribution model that Microsoft clearly doesn't support.

"Now it becomes possible to divide and conquer our community," said Eben Moglen, an attorney for the Free Software Foundation, the entity behind the GNU license.

By making a pact with Novell, Microsoft also implied that anyone who downloaded or bought Linux from another vendor was doing so illegally.

The next version of the GNU license, currently in draft form, aims to stop similar deals in the future.

Moglen said the draft states that if a company like Microsoft distributes open-source programs protected by the GNU license, it forfeits any related patent claims.

Open-source proponents are frustrated by Microsoft's repeated allusions to patent violations because "they never say what patents being violated, never make any assertions, never put the evidence out there," said Larry Augustin, a technology startup investor who launched SourceForge.net, a prominent open-source development site, in 1999.

But Augustin also acknowledged that it's not in Microsoft's interest to do so: Open-source programmers could rewrite their code to avoid infringing on specific patents, or the courts could find that Microsoft's patent isn't valid.

If Microsoft were to start suing, it could also kick off a patent war on a grand scale.

An organization called the Open Innovation Network, funded by IBM Corp. (IBM), Red Hat Inc. (RHAT) and others, has amassed a vast number of software patents.

In the event of a Microsoft lawsuit against open source companies or customers, the OIN would retaliate in kind.

"We believe it's highly likely that Microsoft would infringe some of our patents," said Jerry Rosenthal, OIN's chief executive.