Apple - Is it possible to run Nautilus on OS X?

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).

[EDIT] When I originally wrote this answer, there was another answer and a few comments that dealt with the issue of running Nautilus instead of the Finder: in other words, how to prevent the Finder from running at all. Given that context, my answer as written in its original form clarified and/or provided an alternate method.

It appears that the original author has now removed that answer and the related comments. Without that answer to provide a context, I can understand how my original answer may seem to be coming out of nowhere (hence the downvotes?). I'll try to rework it to provide the necessary context that the deleted answer helped to create.

While Josh's answer regarding MacPorts addresses how to install nautilus, it doesn't address how to run it "instead of Finder".

In the other answer(s), there seemed to be some confusion about whether it would be possible to prevent the Finder from running.

Unlike an application such as the Dock, the Finder isn't considered a "required" application. For example, if you were to write an AppleScript to the effect of tell application "Dock" to quit"and then run it, the loginwindow would immediately re-launch the Dock, since it assumes the Dock must always be running. With the Finder, however, as long as you quit it in a way that allows OS X to know that you had a clear intent to do that, the loginwindow won't relaunch it.

To do that, all you need to do is simply tell the Finder to quit rather than trying to kill it. When you kill the Finder forcibly by using the Force-Quit option or by using kill or killall in Terminal, loginwindow (or launchd for your user account) will immediately try to relaunch it because it saw that it terminated "unexpectedly".

Telling the Finder to quit via an Apple Event won't result in it automatically being relaunched.

An AppleScript like the following could be run at login to quit the Finder:

property runningApps : {}
property assureQuitMenuItem : true

tell application "System Events" to set runningApps to name of every application process

if (runningApps contains "Finder") then
    tell application "Finder" to quit
end if

if (assureQuitMenuItem) then
    set quitMenuItem to missing value
    try
        set quitMenuItem to (do shell script "/usr/bin/defaults read com.apple.finder QuitMenuItem")
    on error
        set quitMenuItem to "0"
    end try
    if quitMenuItem = "0" then
        do shell script "/usr/bin/defaults write com.apple.finder QuitMenuItem 1"
    end if
end if

A saved version of this in application form is at: QuitFinder.zip

(You can open the application in AppleScript Editor to see its contents by dragging the script app icon onto AppleScript Editor's application icon).