Apache Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies and developed by the Apache Software Foundation (ASF).
The JBoss Enterprise Application Platform which is also known as JBoss EAP is a open-source Java EE-based application server runtime platform and is part of a wider portfolio of software known as the JBoss Enterprise Middleware portfolio.
WildFly, was better known as JBoss AS is an application server created by JBoss, but now under continuous development by Red Hat.
Resin is a web server and Java application server created by Caucho Technology.
Jetty is a Java based HTTP (Web) server and Java Servlet container and is developed as a free and open source project as part of the Eclipse Foundation (originally it was developed as an independent open source project).
Jetty 设计了非常良好的接口，用户可以非常方便地对 Jetty 的某些实现进行修改，使得 Jetty 适用于特殊的应用程序的需求。
WebSphere 是IBM的。两者生态圈略有不同。比如IBM还有IBM MQ，IBM BUS等，Oracle也有类似的方案。