I'm not sure what else I can offer. To access PSQL data, you have two options: Btrieve or Relational. If you use Btrieve, you need to know the exact record structure down to the byte and parse the record in your application. If you use the Relational interface (ODBC, OLEDB, etc), you need DDF files.
In both cases, you need a PSQL engine and possibly a PSQL client. The client is needed when accessing remote data using a server engine.

Once you choose your method, I might be able to offer better suggestions.