First, you're using "open" in a way I haven't heard before (not in the context of "open web"). Not saying it's wrong :) Perhaps we should use it that way too. But you're suggesting a new perspective here. We could debate that first, before debating the technical stuff. Or perhaps we could call it "technologically open."

But to focus on the more interesting technical stuff: First, we have a fast Lua VM port. Not LuaJIT, but even the Lua VM itself is quite fast for a dynamic language (and the port is 2/3 of native speed).

Second, there are experiments with JITs targeting JS, like pypy.js. Yes, pypy.js has a large footprint, as you referred to. But I think the fact is that very little effort has gone into this. Much more is possible than has already been done.

If we had a large, serious project doing this, I think we could see the potential. Instead, things like pypy.js are spare-time projects of a single person. So it's not fair to assume that their success or failure in terms of performance and footprint is indicative.