Yes, CtAPI (Citect SCADA API) allows access to Citect SCADA I/O variable tags via a DLL interface. This allows 3rd party developers to create applications in C ( or other languages) to read and write to the I/O Devices, to use data query and to call Cicode functions.
There is no additional license required to use CtAPI.
There is no additional license required to use CtAPI.