You might start looking for an open source directory server solution around the globe an here we present you one of them. We are talking about OpenDJ which is currently developed by OpenDJ.

OpenDJ is open source LDAPv3 compliant directory service, developed for the Java platform, providing a high performance  and secure store for the identities managed by your enterprise.

Just for your history records OpenDJ is a downstream build of the OpenDS project, with a different name to avoid trademark issues. OpenDJ comprises of an open source directory server, client tools, and an LDAP SDK. All modules are 100% Java based and require at least Java 1.6.

You can download OpendDJ from http://forgerock.com/opendj-downloads/ the current version as we speak is the OpenDJ 2.5