RE: Free Simulator?
No, too much electronics involved in changing the PPM signal to a serial USB signal.
The two are totally different.
At the very least some sort of pic type interface is required...
The PPM to regular serial only works practically because of a fluke in that you can use software to make the PC understand the pulses by directly controlling the Serial Interface Controller.
With USB you don't have this fine a level of control over things.