GlassFish

Overview:
In June 2005, Sun launched the GlassFish project -- an action that opened to the Java community the development of an application server that will be compliant with Java Platform, Enterprise Edition (Java EE) 5. Since then a large and growing community of developers has actively participated in the project.

Community:
The GlassFish community currently includes over 1100 members participating in the GlassFish project, with the objective of developing an open source application server that implements Java EE 5. In addition, the community is working to develop various web services technologies apart from the application server development effort. The community includes independent contributors as well as contributors from various organizations and companies. Members of the GlassFish community don't necessarily have to take an active role in developing code for the application server. By simply using the application server, they can file and track bugs and exchange information with other community members.

Projects:
The GlassFish project is a structured environment for developing the open source application server. The establishment of the GlassFish project is part of a larger effort by Sun to release major portions of its code into open source for use and improvement by the community. The GlassFish project is one of a variety of community-based projects hosted on java.net.

An open source application server:
GlassFish community is building an open source application server within the GlassFish project. The open source application server is based on the source code for Sun Java System Application Server Platform Edition 9, donated by Sun Microsystems, and on source code for TopLink, a Java object-to-relational persistence architecture, donated by Oracle. The GlassFish community makes periodic builds of the open source application server available for download.

About GlassFish Project:
GlassFish puts a free, open source, commercial-grade implementation of Java EE 5 in the hands of the community -- and puts it there early. Think about what benefits this might have for you. If you develop enterprise Java applications, being a GlassFish community member gives you an early opportunity to develop those applications and test them for conformance to Java EE 5. Note that conformance to Java EE 5 cannot be assured until the Java EE 5 specifications are final.
If you maintain enterprise Java applications, you can get an early start in migrating to Java EE 5. You can also get an early look at some of the new features in Java EE 5, such as the new Java Persistence API, the enhanced mapping capabilities in Java Architecture for XML Binding (JAXB) 2.0, the simplified interface for web services development in the Java API for XML Web Services (JAX-WS ) 2.0, as well as the ease-of-development improvements in Enterprise JavaBeans 3.0 technology. You can try out some of the new features in applications that you deploy to the GlassFish application server.
Another significant way in which community members contribute is by exchanging information. Whether it's through postings on the GlassFish discussion forum, broadcasts to mailing lists, or blog entries, members of the community maintain a continuing dialog about many aspects of the project, such as personal insights about GlassFish features, project-development issues, and answers to technical questions. Additionally, The Aquarium, a group blog, collects news related to the GlassFish community from a variety of sources. These communication channels provide a free-flowing information pipeline between members of the GlassFish community, including Sun and Oracle engineers.
GlassFish also gives community members the opportunity to improve the application server code. Developers have told Sun that they want the ability to contribute fixes and new features to Sun's code. The GlassFish project gives community members the context to do just that. As a member, you can identify bugs in the GlassFish code, contribute fixes, and even add new features.



References:
http://java.sun.com/developer/technicalArticles/glassfish/GFBasics.html