I'm no expert, but here's what I found in my situation. Since HDCP is a copy protection standard for HD, it protects against having a device inserted between your HDMI component that plays the copy protected material and the equipment that displays it through an HDMI connection. HDCP only applies to a digital connection like HDMI (maybe DVI too, though not sure)
In my case I discovered this when I installed a Yamaha RX-V1600 receiver that has 2 HDMI inputs and an HDMI output. My Comcast box works perfectly when directly connected to the TV but displays a copy protection error on the Plasma display when the receiver is in the way. I guess the theory is that the HDMI receiver can re-direct the copy protected material to a recording device.
I don't know of a way around this.
As far as a Playstation or Powerbook....I doubt that HDCP would be utilized to protect that stream. I know there are other copy protections in place, so you can't copy the software, but intercepting the video stream of gameplay should not require the same HDCP protection but I don't know for sure.