Initial WeakIdentityHashMap.java was taken from apache-cxf project (from what I could find). That project/file is pure ASL 2.0. As per ASL 2.0 requirements the license text & NOTICE file itself have to be redistributed with each source/binary distribution.

Ideally the jar files themselves would contain the license & notice files so that users of jna comply with ASL. If nothing else then I believe at least following steps are necessary:

• Include a NOTICE file mentioning where WeakIdentityHashMap.java is coming from and its license
• Extend wording in LICENSE so that downstreams are aware of need to distribute ASL license when they redistribute