JBoss started as a Java application server (AS). At some point it got much bigger and now is more like the Apache community. Lots of projects like Hibernate and Infinispan are part of it.
In the AS side of things, there were already 2 kinds of releases. Like Fedora, you have the 6 months(?) releases supported by the community and then, from time to time, you get the stable Red Hat EL to be used by clients with support contracts. WildFly will be much like fedora in this sense. Jboss AS will continue for the ones with support contract.
Until now, if you used JBoss in a serious task, there was almost no difference in the quality between paid and unpaid versions, from now on, I think it will be a different story.