Xbox Smartglass does not install for another user
Some apps cannot install for multiple users. Searching the developer forums, the only suggested solution is to contact the app developer (Microsoft) and ask them to test and enable multi-user support.

Technically, it is likely only a small issue like hard-coding where user-data should be stored and accessed instead of using the system provided path variables. Very trivial to fix once the developer is aware of the issue. If the app as open-source you could probably have done it yourself.