&#62;It's not an operating system, because it cannot operate the system (your system being the Computer)<p>Be that as it may (I haven't fully checked out the source to this thing, so I can't say if it could "operate the system" or not), there's nothing preventing anybody from writing an operating system in (mostly) Javascript.  You'd just have to have a JS interpreter built into your kernel.  Now, why you'd want to do that other than for pure hack value, I cannot say.  Nonetheless, it can be done.<p>Edit: You could also (theoretically) have a specially microcoded system that can directly run some form of Javascript bytecode, as was done with the old Lisp machines.