The Apple Schema info is included on Mac clients and servers in:
/etc/openldap/schema/apple.schema
In my experience you can't just drop that schema file into an
OpenLDAP install and have it work seamlessly. You'll need to massage
it a little so that some entries are uncommented and others are moved
higher up in the file.
afp548.com covers the details a little bit more here:
slapd will nicely report the errors for you, and it's not that
difficult to work out how to edit the file so that it's just a matter
of dropping it in. I have a copy from an Ubuntu OpenLDAP install that
I've been working with lately if you can't get it going.