The FileMaker ODBC driver should be installed on a client machine to allow connecting to FileMaker Pro or FileMaker Server Advanced as an ODBC data source.
In other words, the driver has to match the data source. If you want to connect to a non-FileMaker data source, you'll need a different ODBC driver. The Actual Technologies drivers are the only supported choice for a Mac if you want to use FileMaker's ESS feature to connect to MySQL, Microsoft SQL Server, or Oracle.
The complete list of certified drivers for ESS can be found here: http://www.filemaker.com/support/technologies/sql.html