NextShout-XF is a project mainly written in PHP and JAVASCRIPT, it's free.
XenForo version of the NextShout shoutbox.
XenForo version of NextShout.
NextShout-XF is licensed under the New BSD license (http://www.opensource.org/licenses/bsd-license.php), mostly because GPL probably wouldn't be compatible with the commercial XenForo package, but also because I'm just a nice guy. :)