from this link
http://www.penny-arcade.com/report/a...t-some-details
quote extract (from above link)
So that answers one question: Microsoft doesn't seem to care whether or not the ten people in the group are actually family members. They can be friends, roommates, boyfriends, girlfriends, your dog's groomer… you pick ten people, and you share games with them.
The question is how many people can play the game at the same time. Spencer told me he believed that two people can play one copy of a game concurrently, but he urged me to check Microsoft's official wording on the matter to be sure. This is what the licensing page states:
Just like today, a family member can play your copy of Forza Motorsport at a friend’s house. Only now, they will see not just Forza, but all of your shared games. You can always play your games, and any one of your family members can be playing from your shared library at a given time.
So one family member can play a game at a time, but can I be playing the same game? If I buy one copy of a multiplayer title, can I play it in co-op with my son if I own two Xbox One systems?
“The only limitation, it seems, is that only one person can be playing the shared copy of a single game at any given time,” Ars Technica reported after speaking with Microsoft Xbox Chief Marketing and Strategy Officer Yusuf Mehdi. “All in all, this does sound like a pretty convenient feature that's more workable than simply passing discs around amongst friends who are actually in your area.”