Esri Geoportal Server is a free, open source product that enables discovery and use of geospatial resources including datasets, rasters, and Web services. It helps organizations manage and publish metadata for their geospatial resources to let users discover and connect to those resources. The Geoportal Server supports standards-based clearinghouse and metadata discovery applications.
Installation requirements: http://sourceforge.net/apps/mediawiki/geoportal/index.php?title=Preinstallation
I did successful implementation in my place-work using Apache Tomcat and Oracle database so if you have any questions do not hesitate to ask.