That's not true. Yes, it's worth considering outside of the JVM if being on the JVM means your application isn't interactive enough (startup speed doesn't matter for long running, fire & forget tasks).

At the same time, splitting your application into a client/server architecture is not a hack but an engineering decision. There are times when this decision is natural e.g. Music Player Daemon (MPD)[1]. For most CLI applications, there's no clear benefit (but the general approach has no clear downside either - the code overhead of this approach can be brought very low).

Certainly, in a production application you would want to secure the messaging channel (Nailgun doesn't).

[1] A music playing server: http://www.musicpd.org/. Some of the clients happen to be command line: http://mpd.wikia.com/wiki/Clients#Command_Line_Clients

Well, that would do it. =)