Thanks, Todd, for reviewing and testing the extension!

The Terminal.py extension patch provided here is outdated. There have been some minor tweaks and bug fixes that can be found in the IdleX project which works under 2.x and 3.x with the same code. (For example, I removed an unnecessary reference to the history object in the latest version so that I could better support IPython). I know that the IdleX version works under Linux, Windows, and MacOSX. 

Unfortunately, on MacOSX, the "Options" menu may not be present which breaks the loading of Terminal.py. IdleX re-introduces the Options menu on MacOSX if it is missing. I will create a separate issue for the Options menu.