If you are having a problem getting the Darwinports package of the Meld visual diff tool running on your Mac try these two commands before re-running the program.

sudo launchctl load -w /Library/LaunchDaemons/org.freedesktop.dbus-system.plist
sudo launchctl load -w /Library/LaunchAgents/org.freedesktop.dbus-session.plist

The error I was getting before was this:

Xlib: extension "RANDR" missing on display "/tmp/launch-RsRIqw/:0".
Dynamic session lookup supported but failed: launchd did not provide a socket path, verify that org.freedesktop.dbus-session.plist is loaded!
Dynamic session lookup supported but failed: launchd did not provide a socket path, verify that org.freedesktop.dbus-session.plist is loaded!
Dynamic session lookup supported but failed: launchd did not provide a socket path, verify that org.freedesktop.dbus-session.plist is loaded!
Dynamic session lookup supported but failed: launchd did not provide a socket path, verify that org.freedesktop.dbus-session.plist is loaded!
Dynamic session lookup supported but failed: launchd did not provide a socket path, verify that org.freedesktop.dbus-session.plist is loaded!
Dynamic session lookup supported but failed: launchd did not provide a socket path, verify that org.freedesktop.dbus-session.plist is loaded!
Traceback (most recent call last):
File "/opt/local/bin/meld", line 109, in <module>
meldapp.main()
File "/opt/local/lib/meld/meldapp.py", line 855, in main
app = MeldApp()
File "/opt/local/lib/meld/meldapp.py", line 528, in __init__
self.prefs = MeldPreferences()
File "/opt/local/lib/meld/meldapp.py", line 465, in __init__
prefs.Preferences.__init__(self, "/apps/meld", self.defaults)
File "/opt/local/lib/meld/prefs.py", line 91, in __init__
self._gconf.add_dir(rootkey, gconf.CLIENT_PRELOAD_NONE)
glib.GError: Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash. See http://projects.gnome.org/gconf/ for information. (Details - 1: Failed to get connection to session: Not enough memory)
</module>