PPBB is still up and running.
http://ppbb2.ppbb.com/phorum/index.php
The site did go down briefly a month or two ago. Several of their members worked together to relaunch the site with a new format but keeping the old feel. They also took donations as the reason it was shut down before was the cost and time involved.
It is a unique board. Some of the threads grow to epic proportions.
I visit it everyday.