There's another way to run two (or more) instances of any Mac OS X application that doesn't involve making a copy, or any Terminal tricks. All you have to do is right-click (or control-click) the app, choose show package contents, navigate through the Contents and MacOS folders, then double-click the executable you see in there. This will cause the Terminal to open, which will then launch the app. Double-click the executable again, and a second instance of that application will launch (opening a second Terminal window in the process). One gotcha: If you close the Terminal window, the application you launched in this way will quit!