I am also wishing to add own cloud to my companies lion server.
Did you manage to install and run mamp successfully on the server,
Do you know if its possible to install owncloud without mamp, just using the lion server settings.
I have installed owncloud on OSX server 10.5.8 and it works fine with LDAP. The issue just now is the connection with MySQL. Why using MAMP? You have an excellent platform within OSX server.
Just install it in on OSX and enjoy!
User login filter: uid=%uid << Don't miss.... on OSX
User list filter: objectClass=person <<< Don't miss....
Of course you must use Host: 127.0.0.1 if you have set up LDAP correctly..