Hello Processing folks!
I ran into an error running the Open Kinect examples with Processing 4 (on Mac): NoClassDefFoundError: /com/sun/jna/Library.
The issue seems to be with jna.jar.
The Java/Contents folder has jna.jar and jna-platform.jar, these are not in the core/library subfolder. Copying these to the core/library subfolder solves the problem.