Quoted from Crash:
DMD Extender does use copy protection. The keys for a given SD card are locked to that SD card. The Linux partition is hidden and will not be copied using Explorer. Use a program like Win32 Disk Imager to do this. Write down the serial number and keys used on each card! If you screw this up the software will not work and you will need David to clear it up for you. I would take extra precautions since he is unavailable for the foreseeable future.
I have no idea why pintastic thumbs downed your post, it's 100% fact. The DMD extender uses the SD card serial number to generate a unique key. If your SD card dies and David can't provide you a new key for a new card, your DMD Extender is completely non-functional. If you don't believe me, just copy your SD card contents onto a new card and try it out. All you will get is an error message and nothing else on your LCD screen.
I really hope that Dr. Pinball would consider unlocking his software. You have to buy his adapter so what does he have to lose by opening it up? I don't even want to touch my SD card for fear that it may get an unlikely static discharge rendering my entire DMD extender useless :/