Mozilla's Firefox OS is continuing on in development, and a significant milestone has been achieved: Mozilla has announced their Firefox OS developer preview phones. The phones are being developed by Geeksphone in partnership with Telefonica, a major Spanish broadband and telecom provider with worldwide operations, including the US.
The phones do not have top hardware, but that is not the point of a developer preview. They have a CPU Qualcomm Snapdragon S1 1Ghz processor, 2G and 3G network support, a 3.5" HVGA multitouch display, a 3MP camera, microSD, micro USB, all the usual sensors and come unlocked.
Firefox OS is designed for standard HTML5 apps and Mozilla is marketing to developers in part as an appeal to keep standards alive and relevant. In this they are swimming against a tide of HTML apps which rely on proprietary extensions in the Webkit browser engine used by Google and Apple. Microsoft's Internet Explorer on Windows Phone has run into some of the same compatibility problems that Firefox OS can expect.