Hi Colin,
I'm not exactly sure what you mean by digital cordless phone, I'm assuming you just mean a regular 2.4 or 5GHz cordless phone, but as long as it can plug into a standard RJ45 (regular phone line) I don't see why it wouldn't work. They may be trying to steer people away from useing wireless phones that might interfere with the Wifi, I'm not sure.
If by digital phone you mean VoIP then I have no idea. I'm sure you could plug it into the router in your room, but I don't know if it would interface with the Case provided number. Hope this helps.
PS. A phone is not required, it's only if you want one. Of the hundreds of people I know, only about 5 of them have a landline.
Tyler S. Allen
Case Western Reserve University
Orientation Leader, '07, '08
Mechanical Engineering, 2010