How is V8 wired into Chrome, or Rhino(?) into Firefox, for example? Is there a great technical barrier to making it possible for the user to install an interpreter of their choice? As I understand the course of the browser's history, it already seems to be moving to an OS-style program (or, in Chrome's case, it has BECOME an OS), so it seems like user-loaded language runtimes OUGHT to be on SOMEONE'S mind. And I'd be surprised if it hasn't already occurred to someone before, I just don't know the history.
Has anyone attempted to write a browser that allowed for such a thing? Or has JS just been the accepted scripting language, and no one has yet tried to push past?