It is not a JEE application server, rather a platform for developing and deploying Web services, using any standard Java application server out there. WSO2 WSAS is a truly open source product released under Apache License v2.0
The key feature is the management console. You also have the benefit of world class development and production support from WSO2 Inc.
It is battle tested, production hardened and quality guaranteed.
Try it today and experience the power of SOA tooling from WSO2.