Licensing question

Hello,

after couple of months of research and testing PostgreSQL on Windows has
proven to be an excellent RDBMS for my purposes. Now that i've solved most
of the technical problems in the PostgreSQL-Cygwin-Windows chain, one
question remains:

if i deploy PostgreSQL with a commercial application, using Cygwin for
PostgreSQL, do i need to purchase a license or should my application
comply to Open Source specification? Can i avoid the need to purchase a
license or to go Open Source by, for example, launching Cygwin and
PostgreSQL as services, without any contact between my application and
Cygwin, only connecting to PostgreSQL through JDBC?

Cygwin home pages are unfortunately very obscure when it comes to
licensing (and they aren't replying to questions on the subject...). In
many places it says it's GPL, but from elsewhere in the site you get a
very different picture. I asked an expert and even he couldn't come up
with a certain answer right away. I found these two messages from these
archives:

http://archives.postgresql.org/pgsql-cygwin/2002-02/msg00118.php
http://archives.postgresql.org/pgsql-cygwin/2002-02/msg00119.php

.. and these look very promising. However, i'd be grateful for any more
detailed information on the subject and the conclusion. When it comes to
licenses, one can't be too careful :)

Thanks in advance,

- Andy -