Sorry, I was reading our web page and was thinking about how it's programmed. Here's what we say about programming the GY520:

http://www.futaba-rc.com/gyros/futm0807.html

"2 Ways To Program!

Directly, using the GY520's push-button and 2-color LED.
Remotely, using a PC and the optional CIU-2 USB interface. Both required. Click here to download PC software (zip file)."

If you want to program it, you'll need the GYLink software and a CIU-2 USB interface. You need to connect the gyro to the computer via the CIU-2 interface. You cannot plug the gyro directly into the computer.

The instructions for the PC-Link software detail how to set the GY-520 to the S-Bus. It's on page 8.

If you're going to run it on S-Bus, it looks like you have to connect an S-bus output to the gain channel, and an S-Bus output to the rudder channel. The CIU-2 interface and GYLink software are used to set which channels of the transmitter will be sending gain and rudder information.

However, the instruction manual for the gyro, itself, doesn't say anything about the S-bus. We'll ask Futaba for some clarification on this.