Is this a re-packaged v7 [0] (it's from Cesanta as well)? mjs.c is 477K. It looks like it as v7.c is 475K [1]. It shaves whole entire 1MB from my staticly linked builds (v7 1.9MB vs. mjs 998K), and almost 2MB from dynamically linked builds (v7 1.9MB vs. mjs 99K) on amd64. If it shares the same underlying architecture and api [2] then this is a pretty great achievement.
In their docs, they claim 25K storage and 10K RAM. Blog post claims 25K storage and 1K RAM.
[0] https://github.com/cesanta/mjs/blob/master/mjs.c