To clarify, SQL Backup is licensed per machine; but this licensing only applies to the SQL Server instances running the SQL Backup server components. The SQL Backup GUI can be run on as many machines as you like, without requiring additional licenses.
This means if you have one SQL Server, and 10 DBA's connecting remotely to it; you will only need the one license.
If you have any more questions about licensing, the best people to talk to is our Sales team, who can be contacted at firstname.lastname@example.org
Hope that helps,