This week's book giveaway is in the NodeJS forum. We're giving away four copies of Serverless Applications with Node.js and have Slobodan Stojanovic & Aleksandar Simovic on-line! See this thread for details.
Typically a Java application loads a class the first time it is referred to by code which is running. And note, it's classes which are loaded, not libraries. It would be terribly wasteful, both of time and memory, for a Java application to load all of the classes in a library as soon as only one of them is required.
I have no reason to believe that JBoss works differently than any other Java application in terms of class loading; I would be thoroughly amazed if it loaded classes before they were needed.