When running karaf without JAVA_HOME set, but having the JDK installed returns the following warning:
WARNING: Running karaf on a Java HotSpot Client VM because server-mode is not av
Install Java Developer Kit to fix this.
For more details see http://java.sun.com/products/hotspot/whitepaper.html#client
But since the JDK is installed and found via a reg query, karaf will still startup. I think this check should be moved to after the JAVA_HOME validation is done to avoid this warning.