Yup, you're right, I must have been blind - I didn't see the Eagle file reference and I actually looked. Nuts. I've modified my original post accordingly.
But Digilent is then one of the few companies that publish a schematic for their products, never mind the actual EAGLE files that describe their boards in detail. Case in point, I recently had to take apart a vacuum cleaner from Sears that is run by an Attiny 8. No service manual is published or purchasable (at least at Sears). The best Sears does is to sell you parts, after that you're on you're own (and if the illustrations for repair parts aren't clear enough online, there is a replacement part manual available for $7 plus shipping).
It makes sense to publish a schematic for a prototyping board, but companies have choices re: the level of detail they go into describing the various ports, pins, etc. A full schematic goes a long way towards diagnosing rare issues that may then lead to improvements down the line. A full Eagle file is open-kimono time and basically allowing the world to potentially rip off your design. That business model requires your customers to understand and appreciate what you do vs. buying cut-rate rip-offs from China.
For example, the Maple board is already available as a knock-off, just like the Arduino boards. But some of those derivatives also feature interesting options, such as the Arduino board with a built-in ethernet controller (wiznet), Xbee pins, NRF+ pins - for $29. You can't even get just the ethernet shield for that kind of money. And some vendors like Sparkfun seem to be selling items that very closely resemble open-sourced stuff - see the USB host shield from Oleg as an example.