Is it just a coincidence that 'command' and 'attention' are plugged into PWM pins in the first example? My best guess is 'yes', since I doubt that the PS2 controller communicates with an analog signal. I ask this question because I'm creating my own Arduino shield for a special project, and I want to get it right the first time.
It appears to me that the PS2 controller uses SPI. The hardware SPI pins are:
10 SS (Slave Select) -> ATT (Chip select)
11 MOSI (Master Out Slave In) -> Command
12 MISO (Master In / Slave Out) <- Data
13 SCK (Serial Clock) -> Clock
Hooking things up this way will allow you to use the SPI library and get very fast speeds. Even if you use the other hardware SPI pins you can use any digital output pin for the Slave Select / ATT signal. The only requirement is that Pin 10 be set as an output.
If you don't need high speeds it is possible to do "Software SPI" using any four digital pins. You'd have to look around for example code. It's not much more complex than using a shift register.
I'm going to assume that the PS2X library uses software SPI. Reading through the source code (way over my head), it doesn't import the SPI library but it does a lot of operations with registers.
I just looked at the library code and it appears that it does do software SPI so any four I/O pins should work. Shouldn't need to use the PWM pins if you want to save those for something else.