For information on how to enable the root user in Mac OS X Mavericks, see this tech note from Apple:
http://support.apple.com/kb/PH14281
And for doing the same with OS X Mountain Lion, see this tech note:
http://support.apple.com/kb/PH11331
Finally I have gotten round to finishing the install of BugZilla on OS X Mavericks (OS X 10.9)
and I’m pleased to say it is working well.
There were several hurdles along the way, but the main one which kept bugzilla from running was that the MySql library, required by perl to access MySql was installed in a different place than the _www user group expected to find it.
After installing Perl, MySql and BugZilla the main bugzilla install script kept failing with errors trying to connect to the MySql database.