I'm not sure, but it seems there is a memory leak in KieScanner, not in scanner directly, but somewhere in plexus used internally.
If you start KieScanner with version = LATEST, start it with interval say 1 second and sample memory with visualvm (or any other), you can watch number of instances org.eclipse.sisu.plexus.* growing over time. And they cannot be garbage collected - memory root is timer thread. This happens in drools 6.4.0, in 6.3.0 this issue was absent.
Eventually application fails with OOM.

As a workaround we call KieScanner#scan manually in a separate thread pool that is recreated from time to time.