Since JRuby 1.9 doesn't require posix/spawn, only follow that path if JRuby is loaded and running in 1.8 mode.

lib/foreman.rb

@@ -8,8 +8,8 @@ module Foreman
     File.expand_path("../../bin/foreman-runner", __FILE__)
   end
 
-  def self.jruby?
-    defined?(RUBY_PLATFORM) and RUBY_PLATFORM == "java"
+  def self.jruby_18?
+    defined?(RUBY_PLATFORM) and RUBY_PLATFORM == "java" and ruby_18?
   end
 
   def self.ruby_18?