GlassFish is an open source application server project started by Sun Microsystems for the Java EE platform and now sponsored by Oracle Corporation. The supported version is called Oracle GlassFish Server. GlassFish is free software, dual-licensed under two free software licences: the Common Development and Distribution License (CDDL) and the GNU General Public License (GPL) with the classpath exception.
GlassFish provides the enterprise level reliability and performance with full clustering and has a wide functionality range. It is quite cool in that it allows you to manage the central repository via the admin panel, which supports all features available in GlassFish. However, as you know, more functions = more resources.