Is it possible to run Nautilus on OS X? Is it possible to run Nautilus instead of Finder on Mac OS X Snow Leopard? How?
Looks like it's available in MacPorts, so you could install MacPorts and then install Nautilus using that:

sudo port install nautilus  


You should then be able to run it using the nautilus terminal command.



You may see the following during installation:

############################################################################
# Startup items have been generated that will aid in
# starting dbus with launchd. They are disabled
# by default. Execute the following command to start them,
# and to cause them to launch at startup:
#
# sudo launchctl load -w /Library/LaunchDaemons/org.freedesktop.dbus-system.plist
# launchctl load -w /Library/LaunchAgents/org.freedesktop.dbus-session.plist
############################################################################


Running the commands manually should be enough to run nautilus directly after installation (without rebooting).