The OpenACS documentation needs to be updated. The absolutely recommended way to install PostgreSQL on Debian is through the packages.
The packages handle quite a bit of the initial configuration, do some security tightening, etc. For Debian stable, packages are available from people.debian.org/~elphick/ as posted earlier on this thread.
I have installed OpenACS on Debian woody. I grabbed the PostgreSQL woody packages, grabbed the tcl8.4 package from backports.org (IIRC) and re-compiled the AOLserver package from unstable.
It'd be nice if the AOLserver package maintainer made woody backports of those packages on his people.debian.org area. Maybe he already does.
-Roberto