Yeah, I saw that a while ago.
The thing is that the hack is only for a specific gun. For example if this pedal maps to a button then you can plug two in with two USB guncons and then play double window on one machine/TV with two people for TC 2 and 3. This pedal should work also for PSOne and PS2. You can also link to PS2 machines for true arcade action. Hacking each guncon is a poor way of doing it because they could have just hooked up the pedal to a PSOne PCB and used it as a separate controller.
I'm a big fan of the TC games and I've used joysticks on the ground as a "pedal" secretly wanting something exactly like this.