Elf.js is a project mainly written in JavaScript, it's free.
Simple ELF parser in JavaScript
elf.js: A (very simple) ELF parser in JavaScript.
Relies heavily on typed arrays, as well as: https://github.com/davidflanagan/BufferView and DataView, or: https://github.com/davidflanagan/DataView.js and: https://github.com/luser/uint64.js
Usage: var elf = new ELF(buffer); where |arraybuffer| is an ArrayBuffer containing the bytes of the ELF file.