The last released version of naviserver works with OpenACS (or at least, worked, the last time i have tried it). See here for the changes
https://openacs.org/forums/message-view?message_id=353949The current version of OpenACS does not work due to various reasons, but it is an effort of - i think - less than one week to get it running. Neophytos is running phigita.net on a snapshot of naviserver, but he is not really using OpenACS, but a strongly modified clone. Naviserver is well maintained but a moving target. I said a year ago or so that i will try get OpenACS running on Naviserver, once there is a new release as a reference point.
I do not see a big problem with the current situation of Aolserver. If a real problem shows up, or maintenance becomes a problem, we will move our apps to naviserver.
Going to apache is a long way, and i am not sure about the advantages, esp. when c-code modules from aolserver are involved.