This post is about transforming Elementary OS Freya into OS X Yosemite (only the appearance ;-) ). If you’re on eOS Freya, type the below command into the terminal
Above command will add the latest gnome and elmentary daily PPAs to your system and perform a distribution upgrade. After that type below command in-order to install nautilus and epiphany.
Now you can download the XGtk theme from this link and place the theme folder within /usr/share/theme and apply xGtk using elementary-tweak. Now reboot your pc and if everything goes well, your desktop will look as below.
A huge thank goes to Camilo Higuita for creating this wonderful theme and for providing the instructions.