ok, authentication with LDAP is working now using nsldap from aolserver cvs.
Just set BindAuthenticationP parameter from //yourhost/acs-admin/auth/authority-parameters?authority_id=XXX as empty (instead 1, as described in howto https://openacs.org/forums/message-view?message_id=937445).
With this set up ns_ldap try to retrieve the password from LDAP (attribute: userPassword) and compare it against the password provided by user in LDAP openacs authority.
