GPL Licence

PostgreSQL,

Please help me.  I need to understand how you see the bounderies of the
GPL licence.

I want to use PostgreSQL as the server of a commercial (non GPL)
application.   All PostgreSQL components will be clearly marked GPL with
URL to sourse code, and readable GPL, to the satisfaction of PostgreSQL.

Can you please tell me whether that is acceptable under your
understanding of the GPL?

Specifically, with respect to MySQL take on the GPL, where the use of
API's and lib's are seen as an extension to the main code, and therefore
  all applications must be GPL, or have a bespoke licence, or be illigal.

Or other people who think that the use of API's and lib's form a logical
abstracted boundery between the server and client, therefore not
extending the product, therefore allowing commercial applications which
are not GPL.

Can you please let me know whether we can use PostgrSQL or not?

Thanks,

Ben Clewett.