Thanks for the pointer to the config.tcl docs. I'll look at that closer as I upgrade the site to Openacs 5.x.
I got the OpenACS 4.6.3 site to appear in aolserver4.0 by installing nsxml.so on the 4.0 server, after making sure that I had that libxml2 installed, I added this to the nsxml.so makefile:
CFLAGS += -I/usr/include/libxml2
and did a:
make install AOLSERVER=/usr/local/aolserver40r10