Just a quick summary on libraries that are necessary for reverse engineering of these two databases (when native connection is used).
MySQL db - libmysql.dll
PostgreSQL db - libpq.dll
Except the libpq.dll library, you may also need the following libraries: libeay32.dll, libintl-2.dll, libiconv-2.dll, krb5_35.dll, ssleay32.dll, comerr32.dll.
The libraries are distributed with the PostgreSQL package.
The libraries should be copied to the BIN directory of TDM3. Possible path is:
TDM3 Commercial v.
C:\Program Files\Quest Software\Toad Data Modeler 3\Bin
TDM3 BETA v.
C:\Program Files\Quest Software\Toad Data Modeler - Beta 3\Bin