Arduino PS/2 emulation

I am trying to get my arduino to pretend to be a PS/2 mouse/keyboard. I am following the guide in this page: http://www.arduino.cc/playground/ComponentLib/Ps2mouse

but I'm a bit unsure regarding the cabling. The image is pretty easy to follow if you hook a keyboard to the arduino, but what do you do with the 5 volt line if the arduino is the keyboard? Should I just leave that cable unhooked seing as the arduino gets power through USB?

Should I just leave that cable unhooked seing as the arduino gets power through USB?

Yes. The ground should be hooked up, so both ends agree on what "ground" is, but the +5 supplies should not be tied together.

Ran