KT, Alfresco, OpenDocMan, various other DMSs (Score 2)

You might consider exploring http://www.knowledgetree.com/ (commercial open source) or another DMS like the following:

Alfresco - Open Source Enterprise Content Management (CMS) ... - alfresco.com
OpenKM - powerful, easy to use, web-based scalable electronic ... - openkm.com
Epiware - Document Management Solutions for Everyone. A powerful ... - epiware.com
Document Management Software - Your Search for Document ... - ademero.com

http://www.opendocman.com/ (PHP)

http://en.wikipedia.org/wiki/Category:Document_management_systems