Many people have asked, "why does the world need another application server?" After all there are numerous application servers already, many very capable products, several relatively inexpensive products, and even two other application servers that are J2EE certified -- JOnAS and JBoss.

There are several key answers to this question.

One important answer is that there's still room left for innovation in the Application Server market. Many current application server providers have stopped enhancing their core application servers, focusing instead on other products such as portals and integration platforms. The Geronimo team believes that the application server space is not dead, and there is plenty of room left for innovation. We'd rather build a newer and better application server, and integrate with other projects that provide features like portals and ESBs.

As a specific example of this principle, Geronimo has been built to be modular and configurable to a greater degree than other available application servers. A key aim of Geronimo is to support custom "builds" or distributions of the server, tightly customized to the needs of a specific application or deployment scenario. The core J2EE application server is created by assembling a group from over 40 distinct configuration modules. But for applications with different needs, servers can be assembled from a smaller group of components, or including additional third-party components. The Geronimo Plugin system allows new features to be downloaded and installed or updated at runtime, and it can also be used to copy applications or services from one Geronimo server to another (to get a new developer's environment up immediately, to migrate an application from test to production, or to clone features across a farm of servers).

Another answer to this question is the Apache license. As an open source product, Geronimo is clearly in the same playing field as JBoss and JOnAS. However, both of those projects use the Lesser General Public License, or LGPL. While the exact effect of the LGPL as it applies to Java is subject to interpretation, one thing is clear. Changes to the core product, or products derived from the core product, must also be released as open source under the terms of the LGPL. The common interpretation of the LGPL is that a J2EE application can safely run on JBoss or JOnAS without being considered a derived work. But many development tools and server products could benefit from building on a certified application server, and those often require enough custom interaction with the application server that they may well be considered derived works. It's no surprise that most commercial products like portal servers and integration servers are built on top of proprietary application servers.

In the future, just like some vendors have built proprietary servers which tightly integrate the Apache web server or the Tomcat web container, the Apache license will allow proprietary products to be built using Geronimo as a fundamental building block. The next natural question is, "why would you want some big company to profit from your hard work?" There are many answers to this too, but a key point is that many companies who use and profit from open source servers contribute back to the open source projects. In fact, the first commercial product based on Geronimo has already been released, and the company behind it supports several developers working on the Geronimo project. In other words, each product built on Geronimo looks like a success story, not a hurdle.

License aside, Geronimo is intended to scale in a way few open source products have really explored. Many open source projects are very accessible to developers, but fall short when it comes to high-end production configurations. Clustering support tends to be limited in scalability, and most open source products are very limited when it comes to management and deployment in 24/7 configurations. Integration packages for standard third-party systems such as accounting and ERP systems are typically targeted strictly at proprietary application servers. All of these hurdles need to be overcome, without losing the core ease-of-development features that attracted a following in the first place.

Geronimo will ultimately address these issues, supporting ISPs, high-load Internet-facing web applications, and other applications ranging from small to very, very large. Of course, talk is cheap, and the 1.1 release of Geronimo doesn't include all the features on this list. Still, the Geronimo team members have developed and supported applications in these mission-critical environments, and this goal has been and will continue to be an important one in the ongoing development of Geronimo.