Darling is a tool that allows you to run applications de Mac OS X en Linux.
It is a project in a really green state that for now only supports some application accounts, such as Midnight Commander, Bash and Vim. If you're curious and like to fiddle with —really — new tools, you might want to give Darling a try and try to install some. program of OS X. Of course, you have to compile them.
Like I said, it's very, very green.
With the above in mind, if you want to try the tool developed by Luboš Doležel at Ubuntu 13.04 you just have to add to your software sources Thomas-Karl Pietrowski's "Darling + GNUstep" repository.
To do this, open a console and run:
sudo add-apt-repository ppa:thopiekar/darling && sudo apt-get update
Then simply install the package:
sudo apt-get install darling
The repository is also valid for Ubuntu 13.10 Saucy Salamander. To learn more about the tool you can visit its Official site.
More information - Darling, run Mac OS X applications on Linux
and how can I install in ubuntu 14.10?