You're speaking about the actorSystem or the LogService? (cause I'm not the author of the ActorSystem)
I would say no, it does not need to be volatile. from www.osgi.org/javadoc/r4v43/core/org/osgi/framework/BundleActivator.html : 
" The Framework must not concurrently call a BundleActivator object."
But it's really good pointing that (as, most of the time, I let akka manage the concurrency issues). So thanks to tell me if I'm wrong.