The Yellow JS (not sure about the ES6 one) logo was make by Chris Williams for the community and he has put up a repository for the same : https://github.com/voodootikigod/logo.js
As for the legal rights, Quoting: "We are releasing this under a MIT license so you can print it on anything, use it anywhere, and never have to worry about royalties, licenses, and other such things."
As for the legal rights, Quoting: "We are releasing this under a MIT license so you can print it on anything, use it anywhere, and never have to worry about royalties, licenses, and other such things."