Its in RESTEasy SVN at the moment and downloaded from there too, but I plan to move it to HornetQ's SVN and bundle for next release. That is, if Tim wants it there or not. Same goes for the docbook on it too.
for users interested to provide feedback on HornetQ REST interface, there is also an ongoing discussion on RESTeasy mailing list http://sourceforge.net/mailarchive/forum.php?forum_name=resteasy-developers