DataFlex has several database drivers available based on your license:
Your DataFlex Studio license is "Connectivity Enabled" and includes complete access to all the drivers (without additional licensing or registration), so you can start developing client/server applications now, and at no additional cost.
When you deploy DataFlex applications that use any of the drivers, you must obtain the appropriate deployment license. To make this process easier (and save money), you can purchase your Client Engine and / or Web Application Server licenses "Connectivity Enabled" and have access to all of the drivers.
The DataFlex Client Engine and Web Application Server have the ability to load the driver(s) for any database(s) you wish to use; often without having to recompile the application.
Please consult the documentation for the individual Database Drivers for more information.