Nokia Corp. (NYSE: NOK) says its $411 million buyout of the rest of its mobile operating system partner, Symbian Ltd. , isn't just a way to battle other OS initiatives. It's an attempt to make Symbian's operating system the most widely used software in the world. (See Mobile OS Wars: Nokia Snaps Up Symbian.)

London-based Symbian already has the most popular mobile phone operating system in the world with a market share of around 65 percent, compared to 12 percent for its closest rival, Microsoft Corp. (Nasdaq: MSFT)'s Windows Mobile. More than 200 million phones have shipped with the Symbian OS onboard since the firm started operations in 1998. (See Canalys Reports on Devices.)

"You can see how we get to the next 100 million," Symbian's VP of strategy, John Forsyth, tells Unstrung. "The question then becomes: 'How do we make this the most widely used software platform on the planet?'"

It's going to take a while, given that Windows runs nearly 1 billion personal computers. Symbian and Nokia's hopes hinge on making Symbian's OS available on open-source, royalty-free terms via establishment of the Symbian Foundation.

This would allow Nokia and friends to "shave a few dollars off" the bill of materials for handset vendors, which should help address developing markets, Forsyth says. Meanwhile, establishing an open-source developer base should help the platform retain its market share in more established markets. "Sometimes, internally we've called this strategy, 'defend and descend,'" he says.

Taking Symbian open-source is going to be a massive undertaking -- possibly the largest ever, Forsyth suggests, given the 400 million lines of code in Symbian's OS.

It could take "12 to 24 months" after the Symbian Foundation's expected 2009 launch to bring all of the code base out to the open source community, he says.

The Foundation will still try to update the OS twice a year -- as operators have come to expect from Symbian -- with different task groups focusing on aspects such as the user interface, or software and hardware integration for the platform.

Nokia will be "a major contributor" to the Foundation's technical work, naturally, but "roadmaps tend to be built through consensus," Forsyth says. Contributions will be accepted from all Foundation members, and even current and potential mobile rivals such as Microsoft and Google (Nasdaq: GOOG) will be able to develop applications on the open Symbian platform.

Eventually, this will mean that the stream of royalties that now provide Symbian's bread and butter will fall away, but Nokia is clearly hoping that the deal will open Symbian phones up to a much wider market and developer base.

Despite all the friendship-and-harmony talk, Forsyth can't resist taking some jabs at Microsoft and Google. "If you're charging a royalty for your phone platform, that's just going to be incredibly tough," he says.

Google's Android project bears some similarity to Nokia's plans, but Forsyth is happy to highlight Symbian's "trusted platform" and play up Google's newness at this game.

"I don't think anyone in the market really knows what is going on there," he says of Android. (See Android Slowing Down?)

Nonetheless, Microsoft, Google, Apple Inc. (Nasdaq: AAPL), BlackBerry , and smaller players such as Access Co. Ltd. and the LiMo Foundation are shaping up as the names to watch in phone operating systems for the next decade: a market where a company could be the largest software play in the world without users even knowing its name.

— Dan Jones, Site Editor, Unstrung