This code is taken from http://sourceforge.net/projects/goog-ajaxslt/ and licensed under BSD. It is a google-created xslt engine that comes with a subset of the org.w3c DOM and an XPath implementation. From the home page:

AJAXSLT is an implementation of XSL-T in JavaScript, intended for use in fat web pages, which are nowadays referred to as AJAX applications. Because XSL-T uses XPath, it is also an implementation of XPath that can be used independently of XSL-T. 

This is version 0.4, the latest version available as of this date.

All of the google code is here but we currently use only:

dom.js
misc.js
xpath.js

Unfortunately none of this stuff is scoped to any top-level object, we will probably have to fix that at some point. I've already changes some of the code to work better with dynamic loading via eval()