Mozilla has announced today they're effectively working on the development of their own operating system. Mozilla "Boot To Gecko" is basically a Gecko-based competitor to Google's Chrome OS operating system. "Mozilla believes that the web can displace proprietary, single-vendor stacks for application development. To make open web technologies a better basis for future applications on mobile and desktop alike, we need to keep pushing the envelope of the web to include --- and in places exceed --- the capabilities of the competing stacks in question."
Boot To Gecko will incorporate new yet-to-be-developed web APIs, provide a privilege security model, booting to Android-compatible devices, and applications can choose to port or build applications. The new web APIs will expose new device capabilities as well as that of the operating system, including telephony, SMS, camera, USB, and Bluetooth, among other areas.
The B2G / Boot To Gecko work is currently documented on the Mozilla Wiki
and this mailing list thread
Source code to this Mozilla project is being released in real-time via GitHub
From the discussions thus far, it appears Mozilla Boot To Gecko is looking towards a Google Android base for its compatibility in the mobile device space where they're looking for B2G to be most utilized. The developers also aren't interested in the ability to run native code on the device.