I like Tom's approach, because this would be useful for non-ACS AOLserver users as well as useful for us.
Tom - how much would be involved in finishing your ns_ldap module?
With that complete rewriting the OACS 4 package to use it would be simple.
Jonathan's right in that no one stepped forward to offer to port the OACS 4 LDAP package. Any offers to help out will be accepted.