The Database Connectivity Toolkit as you know is based on ActiveX and therefore can not be used under non-Windows systems. The way this has been done so far under Linux was to actually access the according C API for the database in question directly. I do for instance remember some efforts to access MySQL through its client side C API through the use of the Call Library Node.
I have myself worked on a more generic solution to make a library of VIs to access the ODBC API. This library works actually well on Windows for me but I have not found time to compile and test the underlaying DLL for Linux so far and do not foresee to get around that in the near future.