In the end I discovered that this key is also called the "Application Key" and found a way to remap TO it on the Mac. This thread lead me to the solution:
The trick is to install PCKeyboardHack, which can remap certain keys to any keycode.
There really aren't too many good options available. I chose the enter key on the number pad, and remapped it to keycode 110, which is the PC Application Key. Works like a charm.