JBoss actually embeds Tomat for it's HTTP engine. JBoss contains a
significantly greater amount of functionality when compared to Tomat.
Tomat is for HTTP whereas JBoss implements the entire J2EE stack (EJB,
JMS, etc.) JBoss is pretty much the defacto standard for free J2EE
stacks so if you need that type of functionality then you probably can't
go wrong with it.