If you use the SQL instance that comes with Connect, you don't need an additional license, as that is free. If you use an existing SQL DB that you purchased from Microsoft, you only need 1 license. The purpose of the free instance of SQL with Connect was for those instances where there are just a few usrs and there is no need for a full-scale DB. I would not recommend using it if you have over 100 users.
What are you asking about? The Connect server software does come with a MS SQL DB as part of it, but you don't have to use it, and shouldn't use it if you have a deployment larger than one server.