I tried Cynthia's idea but didn't work. I looked in the aolserver documentation but couln't find any thing. What I did was:
ns_section "ns/server/${servername}"
ns_param UserMapDir public_html
I also tried
ns_param UserMapDir ~/public_html
In both cases I get a page not found.
When loading with openacs I get a security error. I guest the request procesor would be checking if I have permission to go to that dir, so I would have to explicit that all ~public_html should be public.
This is a petty. It would be a nice feature if we want to replace Apache instalations.