GlassFish is a community-supported enterprise software server, a Java EE open source software server. GlassFish provides a small footprint, fully featured implementation of Java EE 6.

1. Free community-supported enterprise software server
2. The best open source software servers in the industry today
3. Next-generation modular and extensible architecture (OSGi)
4. Enterprise reliability and performance with less complexity

The GlassFish Community also delivers many other useful components including reusable modules for JCP technologies included in Java EE 5, like JAXB, JAX-WS, JAXP, StAX, JSP and JSF. GlassFish also includes several popular Web.Next projects like jMaki, Phobos and DynaFaces, many tools, like the Continuous
Integration tool Hudson, and useful infrastructure like Grizzly the NIO-based server framework. The GlassFish community also maintains a Maven repository for all these components.

What makes it different from other products:
1. Support for the latest web services specification in addition to proven interoperability with Microsoft WCF.
2. Support for both older and newer versions of EJBs.
3. Cluster wide management and deployment.
4. High availability both with in-memory replication and persisted replication using HADB.
5. Fine grained monitoring API based on JMX in addition to already available monitoring facilities in its administration console.
6. Support for Ruby on Rails, in addition to PHP support, using Quercus makes GlassFish a suitable software server for hosting heterogeneous applications.

The license of this software is Freeware, you can free download and free use this web server software.