Found this through a google search and eventually figured out a solution. For anyone still looking for a solution to this for mac Apple OSx OS x hope to help some others.
-Open 'Applications' folder.
-Right-click 'Arduino', select "Show Package Contents".
-Open 'Contents' folder.
-Open 'MacOS' folder.
-Double-click 'JavaApplicationStub' to run it.
A Terminal window will open and a new instance of the Arduino IDE will pop up shortly after. Closing the Terminal window will close that instance of Arduino IDE. So minimize it or something. I can run 3 instances of Arduino IDE with no problems, possibly more, I haven't tried.