The ODBC driver will ask for a user name and password only if the 4D password system has been initiated. If you want to keep your own custom password system and at the same time want to initiate 4D's password system to challenge ODBC clients for a user name and password, it is possible.
Make a group for all your users and a default user with no password. Under database properties, 2nd tab, in the 4D Open Access select that group create, and under Default user, select the default user. In doing this a connection coming through ODBC will be challenged for a password while a connection coming from 4D client will not be challenged for a password, allowing your own custom password system for 4D client connections.