This is all whispercasting. From the "howto" video :

"dualchoc is only needed on the PC of the character you want to control"

It is not passing one key to multiple instances, it is responding 100% to whispercasting.

Also, response from VirusTotal :

http://www.virustotal.com/analisis/c...00b-1251448313

Result: 5/41 (12.2%)

And we've talked about this here before apparently :

http://www.dual-boxing.com/showthrea...light=dualchoc