I have a DB server running on a private network behind the webserver. You can change localhost to the remote machine name. You will also need to edit the pg_hba.conf file (/usr/local/pgsql/data/) on the remote machine to allow for remote connections. I believe it is turned off by default. Make sure you start the postmaster with the -i option.
On the OpenACS side, you will need to modify the bootstrap installer to allow for remote connections. By default, it does not pass the host parameter for the db and will not be able to connect to remote machines. I don't know if that functionality has been added to the CVS tree. I can look up the edit I made to if you need.
