CERN as the international European Organization for Nuclear Research has been involved since its early beginnings with the open dissemination of scientific results. The dissemination started by free paper distribution of preprints by CERN Library and continued electronically via FTP bulletin boards, the World Wide Web to the current OAI-compliant CERN Document Server. CERN Document Server Software (CDSware) is a suite of applications which provides the framework and tools for building and managing an autonomous digital library server. In this paper, we discuss the design philosophy of CDSware and its modular, extensible, architecture. Each module comes as an independent entity embodying a specific aspect of digital library workflow. By means of a flow-chart we present the operational workflow of the system, depicting its module interactions. Hence, some of the key features in the CDSware technology are introduced more in detail, namely metadata representation, acquisition and delivery, indexing and ranking techniques, user interface and ersonalization. CDSware uses entirely freeware technology and it is available under the terms of the GNU General Public License. It is developed by the CERN Document Server team and is driven and validated by the CERN Scientific Information Service. In addition, CDSware has been installed and is in use by over a dozen institutions around the world. A brief comparison with other existing free digital repository systems will also be made.