The copy machines you are using are configured in a certain way to use a coin operated slot, key card, or service key (such as those that Kinkos has). Through an interesting "feature" in the firmware, if the copy machine is configured to accept coins or keys, and no machine is hooked up for this, it will give copies for free. Unfortunately, this isn't as helpful as it sounds; anyone with a remedial amount of intelligence who wants to get free copies will try unplugging the instrument first and foremost. As such, it is often impossible without a service key to unplug the apparatus.Link
Fortunately, there is a work-around. Go into "Service Mode" (using star-2 and 8-star), and push the "Option" tab. Underneath it, push "Acc". A new menu will pop up. Hit the "Coin" button, and enter "0" on the keypad. Once you are done, hit "Enter" or "Apply" (you MUST do this after you change any field; otherwise it will reset the next button you push). Once you are done, hit reset until you are on the main screen. Voila - free copies!