If I read it correctly, his goal is to use the PyPy JIT. So what he's doing is translating the PyPy JIT (which is created automatically from the interpreter written in RPython) into javascript. Because he's using emscripten this javascript code can be statically compiled by virtue of asm.js (in Firefox at least).
Yes, he plans to use the PyPy JIT, but it will generate code that is then JITed by the JS engine JIT.
It doesn't require special static compilation to optimize small amounts of JITed code, all modern JS engines can do that extremely well. asm.js is not necessary there.
