For the record, I'm very interested in this as well.
For the previous versions of JBoss AS this always has been troublesome. AS5 had a complete source archive published, but it's internal structure was different from the compiled download. In Eclipse you had to attach each individual jar, meaning it took you several hours to attach source for the most important parts (and if you changed to another workspace, you had to redo all that work).
AS6 is even worse, as the published source archive only contains a small selection of the source that makes up AS6.
Maybe AS7 will be better and hopefully there will be some effort going on to improve this.