Probably not. The NAS device is probably running a stripped-down and customized version of Linux that handles only file and print services. It may be running on non-x86 hardware, but more likely it's running on something low end like a Pentium or Pentium II CPU. At any rate, there doesn't appear to be any viable method of loading the new OS. Presumably this device is configured via a web browser or serial connection. There is likely a method for updating the device firmware (similar to the LinkSys cable/DSL routers) and that some enterprising soul will develop a firmware version with more features, but the odds of making this a true server capable of complex processing this are slim.
At $700 for the box, you're probably better off buying a real server anyways. Sun has a new line that starts around $750-$800, and it would perform considerably better as a server than this NAS box ever could be modified to do.