J2EE systems are, too a large extent, partitioned from the underlying datasource. As long as there exists a compliant JDBC driver the database will most likely be supported - the proviso usually being the mapping relationships for Entity Beans and the supporting database elements. The latest mySQL servers bundled with Red Hat AS should be fine.
JBoss is a pure Java application server. As such, it is not directly CPU dependent. Your Java JDK must support the CPU and the OS. JBoss 3.2.x requires at least Java 2 JDK 1.3.1 (actual release that works varies depending on the JDK provider). It is probably better to obtain the latest JDK (1.4.x).
The only other requirement is a properly configured network service for Linux - e.g. The hosts file is properly edited, the hostname is resolvable and so on.