It seems that as of Java 7 Update 51, unsigned applications are BLOCKED by default. You now have to add a manual exception, as detailed at https://www.java.com/en/download/help/java_blocked.xml
in order to run free routing.net. (Earlier versions of Java 7 will not run it either, they block it on the grounds of java being out of date.)
What really needs to happen is this application needs to get signed, or at the very least, get hosted on an https server, so as to generate less warnings when a manual exception is added.