You can download Sun Java System Directory Server Enterprise Edition 6.0 software from the following location.
http://www.sun.com/software/products/directory_srvr_ee/get.jsp
The download page serves as a starting point to direct you to the proper downloads depending on the distribution type you need to download. Directory Server Enterprise Edition 6.0 is available in the following distributions.
The Sun Java Identity Management Suite distribution contains the native package distribution that is provided as part of Sun Java Enterprise System. The Java Enterprise System distribution does include Directory Service Control Center.
The zip distribution is not based on native packages. The zip distribution does not include Directory Service Control Center.
For a comparison of the two distributions, see Directory Server Enterprise Edition Software Distributions in Sun Java System Directory Server Enterprise Edition 6.0 Installation Guide.