JBoss is community driven so it is completely free?
and
JBoss itself works within kernel space or user space
+1 A:
JBoss is a company, not a product, and is a subsidiary of RedHat.
JBoss Application Server is open-source and is released in unsupported community edition, as well as commercially-supported Enterprise Application Platform edition.
Like any java application, JBossAS runs in user space.