MS SQL
WinDev has both OLE DB and native support for Microsoft's SQL Server.
Licensing
There was a lengthy discussion recently in the WinDev Skype chat about licensing issues. Key points from that discussion:
A license is needed for the native driver - if you don't want to deal with the licensing issues, and you don't have a need for the native driver's better performance, you can always use OLE DB which is generally equivalent to Clarion's MS SQL driver
Licensing is per physical server, and lets you access as many database instances as the server can handle.
Unlike SQL Server, there is no charge for native access to Hyperfile, MySQL and PostgreSQL.
No dongle is needed for the server