Originally Posted by Cndctrdj
If it is installed on the Xbox one it's licensed to all the players on that xbox. So that shouldn't matter.
My suspicion is that it will work 'sort of' like it currently does on the Xbox itself. The gamertag that buys the game will have the license associated with it, and the 'home' console will have the game associated with it. In the case of windows 10, the home 'console' will be that user that currently is signed in on the PC (as the licenses will be tied in to the windows store user that is active).
I know this works, because my daughter bought Minecraft windows 10 on her account. I was on her computer goofing around, and was playing with the Xbox app on her PC, and I changed the user to my gamertag. I forgot to 'sign out' of the Xbox app, and just closed it. The next day she was playing Minecraft and she assumed it was on her account, while I was playing on the Xbox one some other game and I kept on getting achievement unlocked notifications for Minecraft windows 10. Thus it seems that your gamertag can be active on multiple devices (Xbox 360, Xbox One, Windows 10 (and windows 8.1), Windows phone) simultaneously. Just for the heck of it I decided to unlock achievements on all 4 devices while being active on all 4 (playing different games), and it worked. With GFWL, you would get disconnected from the Xbox 360.
Now the only caveat to that is that if there is going to be cross platform play, I do not think it will be possible to have the same gamertag active on Xbox one and PC. If the servers are going to be different it might be possible. However with different gamer tags, you should be able to play the same game on 2 devices with 1 license.
The only thing that I have not checked is whether she can play (Minecraft or other Windows 10 games) on another PC while I am signed in on her PC and playing the same game. Theoretically it should be possible.