the name "META-INF/init.rb" is a bit unfortunate. the jruby-rack uses this file and "WEB-INF/init.rb" to configure the application be it gets executed by just requiring them. so an executable war file can not use META-INF/init.rb since it gets required when jruby-rack boots the webapp
since jruby-rack uses these files as well warbler does the same, I did follow this pattern with jruby-mains.
to keep META-INF/init.rb as default start script might work with jars but will have probably undesirable effects on executable/runnable jars.