I just emerged blackdown-jre-1.4.2.03 and tried to run a .jar file. It wouldn't run, because it couldn't find the executable. After I ran ln -s /opt/blackdown-jre-1.4.2.03/bin/java /usr/bin/java, it worked just fine. Is this symlink missing for a reason, or...? ~~ Andrew D.
You need to run 'env-update && source /etc/profile' as the post install instructs. This updates the environment to put /opt/blackdown-jre-1.4.2.03/bin on your PATH.