At Mobile World Congress, which begins in three days, Mozilla will finally take the wraps off the Mozilla Marketplace and allow developers to submit their open web technology (HTML5, JavaScript, CSS) apps. While the Marketplace will play an important role in keeping Firefox in step with Chrome, these apps will actually play a far more important role: Boot to Gecko (B2G), Mozilla’s upcoming smartphone and tablet OS, will also use the Marketplace.

For Boot to Gecko to succeed it must have apps, and to create apps you need developers. That’s why, at MWC — according to a source close to the matter — Mozilla will also be announcing that it has partnered up with LG to make a developer-oriented mobile device. Our source couldn’t confirm the specs or the price, but with MWC around the corner we should know soon. Availability-wise, it’s possible that the LG device will go on sale next week, but considering how nascent B2G is — it will probably be usable by the middle of 2012 — it’s important to stress that this is very much a developer device.

Consumers will get their first taste of the Marketplace in Firefox 13, which will feature an app launcher as part of the long-waited Home Tab app launcher. Firefox 13 will be released at the beginning of June, giving developers plenty of time to build apps for both the ‘Fox and B2G.

Now the LG partnership is pretty extraordinary in itself, but that’s not all. Brendan Eich, the creator of JavaScript and the Chief Technology Officer of Mozilla, says that there will be partners, plural, at MWC. Unfortunately our inside source couldn’t give us any information on who these partners might be, but we can make an educated guess: Carriers; carriers like AT&T, Vodafone, Deutsche Telekom, NTT DoCoMo, and many others who have registered their distaste for the proprietary, walled gardens that Apple and Google have been building around their mobile operating systems.

Basically, Apple and Google have so much control over the smartphone landscape that carriers have effectively become nothing more than retailers. Worse than that, their infrastructures have been reduced to that of a dumb pipe, where it is Apple and Google who ultimately decide how the network will be used.

With Boot to Gecko, carriers would have an open operating system, based on an open browser and framework, with a truly open Marketplace. Carriers could create their own Open Web Marketplace and populate it with their own apps, and create their own rules. They could brand the OS and load it up with as much or as little bloatware as they like. With B2G, carriers would once again be in control.

That’s just a tiny, very-zoomed-in glimpse of the future, though. The bigger picture is even more exciting. Basically, B2G is just a cut-down version of Linux that automatically loads Gecko, the rendering engine behind Firefox; in essence, it’s like a simplified version of Chrome OS. Underneath B2G, however, are Web APIs which allow HTML5 and JavaScript to talk directly to your computer’s hardware. In the case of B2G, a Web API lets you make a call using an HTML web page, or access the camera to upload a new photo to Facebook. Because Web APIs are part of Gecko and not B2G specifically, these same Web APIs will exist in Firefox for Android and Firefox for desktop — and because they’re an open spec they could even be implemented by Google in Chrome, or Internet Explorer. Ultimately, the LG coup is big news, but Mozilla has much bigger fish to fry: It’s trying to turn every browser into an operating system.

Read more at Mozilla, or read more about Boot to Gecko