Allowing installation of non Mac App Store applications on MacOSX 10.8 Mountain Lion

I've recently upgraded to Mountain Lion.
Not that I was unhappy with Lion but I've got some feedbacks from developers telling me that there were issues installing one of my applications under Mountain Lion.

Hopefully, there is a simple way to recover your liberty to install the software you want.

The guilty, GateKeeper

The latest MacOSX ships GateKeeper, a small piece of software which prevents users form installing software that do not come from the Mac App Store or is not signed by a registered developer.

What does GateKeeper do?

As long as I saw, GateKeeper doesn't check unix processes.
This means that you can still use homebrew or macports to install for example Cassandra or Hadoop on your Mac.

If you want to execute for example a System Preferences plugin, you need either get it from the Mac App Store or tell GateKeeper to allow Software from any source.


But honestly, if you plan to use exclusively homebrew or macports, then you should seriously consider moving to a GNU/Linux distribution like Ubuntu since the Mac App Store and homebrew/macports stuff are much more developed for a long time there and do not link the user to an exclusive provider.

How to tell GateKeeper to accept software from any source?

Fixing GateKeeper is pretty simple. Here is a 4-steps procedure to follow in order to achieve it.

Locate GateKeeper in the System Preferences. 

In General, unlock the preferences to change the settings.

We selection Anywhere and confirm to MacOSX that we want to Allow From Anywhere.

Now, simply restore the locker to prevent further modifications of the settings.

That's all! Now you have recovered your liberty to choose where you want to download software from.