AIT is licensed under the LGPL version 2. For more information, see the attached COPYING file.
XPath_Parser is currently hosted at GitHub. It’s source code can be found at http://github.com/touv/xpath_parser. PEAR’s package can be found at http://pear.pxxo.net/get/
You can also use the Pear’s Installer :
$ pear channel-discover pear.pxxo.net $ pear install pxxo/xpath_parser