edx/edx-platform — pull request #2793 by davestgermain (2014-03-03 16:16:17+00:00)
Title: Add an option to prevent multiple logins of the same user.

This PR solves MAT-17, by preventing users from logging in through multiple browsers. The feature defaults to off.

@chrisndodge this may be of interest to you
@nedbat