The OpenACS aolserver4 config file is significantly different than the one used in aolserver 3.x
http://cvs.openacs.org/cvs/openacs-4/etc/config.tcl?only_with_tag=oacs-5-2&view=markup
The modules section at the end of config.tcl includes some code and comments about what modules are to be used for which versions of OpenACS and AOlserver.