It's missing the big "Why?" question. I can definitely see why a company like Google would try to create a new systems language, but Mozilla? Its code is already a convoluted mess of old-fashioned C++ code plus even more convoluted XML (last time I looked), rewriting that would be a ginormous project.
So is it more "from some people affiliated with Mozilla" or are they trying to write some new low-level stuff (servers, OS, JavaScript interpreters?)