Based on the available pins on the 30-pin dock connector it is almost certainly a USB keyboard -thee's no pairing so it can't be Bluetooth. In practical terms it would be almost impossible to use it connected to a Mac though - you would need to recable it completely, or make an adapter cable with a female 30-pin connector to USB adapter. Probably it also uses sense resistors on pin 27 (Data+) as Apple likes to use to identify various things like the 10W iPad charger (a sense resistor is what lets the iPad know it is connected to the right charger and allows it to begin charging) and you maybe need to find and remove it to make it appear as a regular USB keyboard.
The pinout for the connector is shown here.
Hey I was just browsing Sparkfun - they have just what you need if you decide to try and build this hack: PodSocket Breakout. It's the female Dock connector (as you would find on the bottom of an iPad).