JDeveloper is an IDE right? But I hear some people mention it as an Application Server. So I am assuming 1).JDeveloper is an IDE which basically comes with Oracle Application Server. 2).Oracle Application Server is in short called as OC4J.
Oracle Containers for J2EE (OC4J) is the J2EE runtime component of Oracle Application Server. OC4J is easy to use and highly productive for developers, while offering outstanding performance and scalability for production environments.
But Oracle recently took over BEA, so BEA WebLogic Server is now called Oracle WebLogic Server. I recently heard an interview (on The Java Posse) with an Oracle guy, and he explained that WebLogic is going to be Oracle's main Java EE server product, and that Oracle Application Server will not be developed anymore.
However, JDeveloper works with different Java EE servers, not only with Oracle Application Server.
1) Jesper already answered this: "Oracle Containers for J2EE (OC4J) is the J2EE runtime component of Oracle Application Server" What whis means is that they are not the same thing, rather OC4J is part of Oracle Application Server.
2) I'll leave this to someone familiar with JDeveloper. I haven't used it for many years so I do not know if the latest version comes bundled with an app server, and I could not glean that information from their product page.
I'm pretty sure that a copy of OC4J came with JDeveloper, although I haven't worked with a recent copy, so things may have changed.
I doubt that OAS is going to just shrivel up and die overnight. It's an integral part of several larger Oracle products. Also, Oracle has the same issues as Sun and IBM about having to deal with legacy systems. They only got rid of Java 1.3 about the time Java 1.6 went live.
An IDE is no substitute for an Intelligent Developer.