To answer Brian's original question: I think the metric works on Windows (Server 2003, 64b): if I am reading the numbers right, it returns the "available" memory which is about the sum of "cached" + "free". So it doesn't suffer from the problem described for  *nix. 

Nevertheless, if we wanted to make this portable we would need somet native/jni code which we try to keep off in WildFly.