Contrary to popular belief Java is highly dynamic. You can introspect the fields, methods, interfaces of any object at runtime, inject new / redefine classes, methods, fields, etc. The problem is that it's very awkward and unwieldy to do so. Hence the tendency to build new JVM languages rather than attempt to use Java's dynamic features directly.
I think "dynamic platform" would be more accurate. Java has typically been a fairly conservative language sat on a much more interesting VM, a VM which has rather more features in common with dynamic languages like Smalltalk than you'd expect.