JBoss application server 5 GA released after a very long period of silence from "JBoss, a division of Red Hat". The new version of JBoss application server supports Java EE 5 and is based on modularity concept with a small kernel named JBoss MicroContainer in the core and all functionalities as modules around the kernel. JBoss kernel is POJO based and all modules follows the same principals, some configuration files are required to configure the services which the kernel will load. JBoss modularity system is niether based on OSGI nor drafts of the to be released Java SE modularity system.
JBoss 5, uses the MicroContainer to ensure an easy implementation of Java EE 6 profiles and also let the developers and administrators to easily disable some features and enable some other features.
I think from version 5, JBoss application server development will see some dramatic changes, the modules will be developed independently and therefore, the release cycle will be a mixed model of hot module releases like updates and patches and major releases which is an integration of all available modules. Although JBoss is far from providing a solid foundation in term providing a package distribution system and all required software to keep an eye on the updated modules and installing them, but that is the path which I think they will follow.
With all this architectural changes, JBoss 5 has a drawback. There is no changes in the administration at all, 3 years of development produces no changes in what administrators use to manage the servers, clusters and applications which are assets of the company which they work for. The same old JMX based administration console is what administrators should deal with for some few months or years until Red Hat finishes the development of their new administration console. Yes, the have a project named Jopr to provide a neat SEAM based administration console, but when it will be ready to get bundled with AS, no one knows.
Today GlassFish is the dominant open source application server and it gained the market share in absence of the Open Source application servers steward, JBoss. The steward re-appeared but its re-appearance is not that promising because of many advantages which its replacement, GlassFish, provides over it.
GlassFish v3 uses a modular architecture based on the standards.The OSGI as the bundle layer and HK2 which is an early implementation of JSR-277, Java SE modularity system, for the service layer. There is no need to edit an XML file, just drop the bundle and it is installed or remove the bundle and it will not load the next time. Also you can utilize the very easy to use update Centre which in addition to managing the currently installed modules, let you install updates or brand new features by selecting the features that you need and waiting for the download to finishes.
GlassFish v3 distribution is based on a solid binary distribution system named pkg(5) Image Packaging System or simply IPS which is a operating system independent software distribution system based on network repository of the software packages. The IPS helps keeping GlassFish up to date automatically with in the blink of an eye. it let you install the new features and updates by some clicks in the desktop GUI, web based administration console, or using the command line
GlassFish v3 provides very solid administration channels including the JMX console, the web based administration console and the command line administration tools which one can use to administrate all aspects of the application server from mere deploying an application to large scale management of a cluster farm.
And Finally GlassFish version 3 supports Java EE 6 and its final version will be available by the middle of 2009. if you want to know about GlassFish for Java EE 5, you should know that the version which supports Java EE 5 released in May 2006 and its 3rd major updates is GlassFish 2.1 which is scheduled to be released on Jan 2009