pg 8.3, oacs 5.7, tcl8.5.11 works well.
I think the emphasis continues to be on keeping openacs releases compatible with the current OS releases for each of platforms.
FreeBSD is a main, stable release platform, because of ongoing, proactive work provided by the wu-wien.ac.at group and others.
I've been unsuccessful at installing openacs on ubuntu under limited time constraints; Apparently, ubuntu is using the releases from Debian, which are stable on Debian, but don't necessarily work well on ubuntu, due to release timing, changing dependencies etc.
The main OpenACS issue seems to be upgrading between pg8.3 and pg8.4, namely dealing with changes in tsearch and perhaps ltree. At least tsearch has been incorporated into the main distribution, changing references and requiring some openacs code changes. I believe there's a thread or two about that. I haven't made the jump to pg8.4 locally, so haven't collected the references for that yet.
cheers,
Torben
