If we purchase the XBOX Live version of the game, with the monthly fee, can multiple accounts play? We have two XBOX Live accounts on one XBOX. Would we need to purchase separate accounts for each player?

If you are talking about the guardians license; they are linked to a players gamer tag. When you buy it you will be able to go online and you will have 4 character spaces to make characters. You can choose to both play on the same gamer tag and share the account spaces, so each of you would be able to make 2 characters. However, if you want to both play on your own gamer tags you will have to pay for 2 licenses.