Balsamiq licenses are based on named users.
A named user/editor is any individual with the permission to create and edit mockups using the application.
Mockups for Desktop licenses are tied to people, not a particular machine. Each user/editor can Install it on any machine they own and use.
In our plugin versions, we call users "editors", to make it clear that you only have to pay for people who create and edit mockups. Everyone will be able to see mockups for free.
A named user with this permission is counted towards the user limit, whether logged in to the application or not.
Our licensing model is not based on concurrent users.
However, you can transfer your users at any time.
See instructions here for transferring or selecting plugin editors: