There's also Samsung's new JavaScript engine "JerryScript":

http://samsung.github.io/jerryscript/

It is truly tiny:

* Can work in less than 64kB RAM

* Doesn't need a full-blown operating system because necessary runtime components (such as libc functions) are provided by JerryScript itself

I think duktape is great http://duktape.org/.

I ran into some issues when trying to use clojurescript with it though.

http://mujs.com/ - MuJS is a lightweight Javascript interpreter designed for embedding in other software to extend them with scripting capabilities. It is written in portable C and implements ECMAScript as specified by ECMA-262.

AGPLv3 licensed? Not really usable for embedding in software..

Why not?

Because your embedded software has to be AGPLv3 licensed as well, a deal breaker for many people, myself included.

For this use case, AGPLv3 is likely no more restrictive than the GPL.

Now that LuaJIT future is getting a bit hazy, it migth be time to consider switching over to a small JS for embedding.

For many. many years I used spidermonkey from mozilla (and it's descendants), but it's no longer small at all, the footprint is pretty big nowadays.

This looks really interesting, though the last update was over a year ago. I"m curious, would it be more efficient to use JSI instead of Node on embedded platforms? Or is there another purpose it serves?

Anyone used one of these as a scripting system for a game engine? I'm still wondering if I should use duktape/MuJS or simply LUA.