>> So the latest RedHat SOA (5.x) is based on jBPM version 3.x? Two major releases back? Is it similar with other components too? I mean such version lag. <<
jBPM 4 was never productized, thus the version lag you mention. jBPM 5 will be officially supported with JBoss BRMS 5.3 which is coming out soon. Until then the only supported jBPM version is as it has been so far jBPM 3.2.