Microsoft is unlikely to sue Linux vendors and users over patents, despite implicatons that a unique deal cut with Novell somehow leaves other Linux distributors open to intellectual-property lawsuits, say experts.

Microsoft and Novell announced an unusual partnership Thursday, involving intellectual property protection as well as an agreement to jointly work on virtualization technology to simplify the process of running Linux on Windows and vice versa. Both companies also pledged to provide sales support for each other's products.

In announcing the deal at a San Francisco news conference, Microsoft Chief Executive Steve Ballmer implied that in signing the patent deal, Novell's version of Linux was safer against intellectual property claims than its competitors' products.

"Novell is acting as a proxy for its customers, and only its customers," Ballmer said. "If they [businesses] want patent peace and interoperability, then they'll have to look to Suse Linux."

Observers, however, said companies don't need peace of mind, since there's virtually no chance Microsoft would sue potential customers, and highly unlikely it would go after a Linux distributor.

"It's more of a competitive positioning statement than a true threat," John Enck, analyst for Gartner, said of Ballmer's chest pounding.

For years, Microsoft has warned companies against Linux, saying that it may contain code that could one day prove to be someone's intellectual property. Unix provider SCO has a $1 billion lawsuit pending against IBM, claiming Big Blue contributed SCO copyrighted code to Linux.

"Microsoft has allowed a cloud of uncertainty to exist around Linux for awhile by making statements that open source doesn't have clear intellectual property," Dave Gynn, application infrastructure practice lead at open-source consulting firm Optaros, said. "In this 'patent peace' thing, what Microsoft is doing is making peace with Novell on its extensions around Linux."

Specifically, Novell's Mono and its use of Microsoft protocols could have presented a problem for Novell, Enck said. Mono provides the technology needed to develop and run Microsoft .Net client and server applications on Linux, Solaris, Mac OS X, Windows and Unix.

That potential problem, however, goes away with the patent covenant the two companies signed, freeing Novell customers from any worries of problems that would arise from a legal tussle.

In general, customers are not targets of lawsuits in patent cases, which are usually between vendors. "What software company on the planet is going to sue someone who might buy their software?" Joe Wilcox, analyst for JupiterResearch, said. "You don't sue your customers." Users of infringing software, however, may have to replace it, or buy a license.

Ballmer's posturing on the patent deal is more likely aimed at rivals Red Hat, a leader in enterprise Linux; and Oracle, which recently said it would launch its own support services for Red Hat Linux, a move that could cut into a major source of revenue for the latter company.

Red Hat believes Novell negotiated a patent deal with Microsoft primarily so Red Hat could market its product as a safer Linux. Red Hat provides protection for its customers through indemnification and an agreement to take care of any technical problems customers may suffer if Red Hat products contained someone else's intellectual property, Mark Webbink, deputy general counsel of Red Hat, said.

"The patent covenant wasn't about intellectual property with respect to Novell, because Novell has its own strong patent portfolio, and Microsoft was no threat to them," Webbink said. "Rather, it was commercial expedient. They can't catch up, and they need something to boost their market position."