I saw this many years ago, but for some reason never finished writing about this. Moxie was a virtual CPU designed to be as simple as possible for the GNU toolchain to target.
Perhaps one of the more interesting things was a port of RTEMS to the Moxie CPU, and a port of Nethack to that architecture. And of course, there was a javascript simulator environment allowing me to easily embed it into this post.
So yes, it’s a virtual CPU, OS & Game, running in java-script and on the page.