In a multi-user Cardbox installation it is quite common to have a mixture of read-only users (who cannot make changes to the database or format file) and read/write users (who can). You can enforce this distinction by means of user profiles, as described in The Cardbox Book (page 253 onwards).
This has licensing implications for large installations, because read-only licences are much cheaper than read/write ones. All standard Cardbox licences are read/write, but you can buy read-only licences in blocks of 5 and add them to your server, or even buy an unlimited read-only licence that does not limit the number of read-only users.
Whenever someone opens a database on the Cardbox Server, the program checks to see what kind of licence is needed and allocates that licence to the user. If the database is being opened with a read-only profile, the Cardbox Server will allocate a read-only licence; otherwise it will allocate a read/write one.
This leads to the question: what is a read-only profile?