Forum OpenACS Q&A: Response to Perl, postgresql in aolserver
The AOLserver community, besides being small, is somewhat fragmented right now due to a lack of a (good) central place for the community to gather around.
Your question in the "Ask Phil" forum is probably take long to be answered because Philip is very busy these days.
The best place (right now) for you to ask questions about your "ns_perl" efforts is in the AOLserver list (http://listserv.aol.com to subscribe). Some folks have embedded the Python interpreter and Java inside AOLserver so they can help you a lot.
About the problem sets, if I am not mistaken, someone "ported" them to PostgreSQL, but my guess it that if you're thinking about working for ArsDigita, only Oracle matters, though that could change bocause aD has shown interest is supporting other DBs.
But if you just want to learn the ACS, using Posgres is more than fine. Oh and BTW Postgres des not have OUTER JOINs yet.