Mozilla is moving ahead with its mobile ambitions, announcing today that it is renaming Boot to Gecko as Firefox OS, while touting support from major carriers worldwide as well as a couple of device manufacturers.

Mozilla’s mobile operating system is entirely open source and its interface is built with HTML5 and CSS web standards, making it extremely customizable. It was recently shown off with a proof of concept interface running on a Samsung Galaxy S II, with Mozilla highlighting its responsiveness to touch input, a 3D graphics demo, a full SMS client and on-screen keyboard, and a store for various web apps.

The first Firefox OS-powered devices will run a Qualcomm Snapdragon processor and are expected to launch in Brazil in early 2013 through Telefonica’s Vivo brand of entry level handsets. TCL Communication Technology and ZTE were revealed as the first manufacturing partners, with operators like Deutsche Telekom, Etisalat, Smart, Sprint, Telecom Italia, and Telenor all committed to offering Firefox OS devices.

Mozilla is hoping to change how developers today must re-write their apps to run on the various closed mobile-phone platforms available, with apps that can run in a browser but still look and feel like a native app with access to underlying phone capabilities like calling, messaging and games.