I'm not a lawyer, but...
The LGPL license allows you to link your commercial application X against JBossCache and ship X without having to license X under LGPL.
This is my understanding, and the understanding of JBoss Inc.
IMO, the LGPL is a bit unclear wrt Java (Stallman wrote it with C in mind). Hopefully, the FSF releases a revised (and clearer) version of the LGPL some time soon.
No, there is no commercial license for JBossCache.
Thank you very much.