Forum OpenACS Q&A: Response to openacs install error: aolserver-postgresql failed dependencies
The aolserver-postgreql package you are missing is the pgdriver. All the RPMS are supposed to be available here. But it seems that location is down for the time being.
I have put up the aolserver-postgresql here on my own webspace for you.
Install that first and you should have no problem installing openacs rpm.
Let's rock and roll.