Paulus from HomeAssistant contacted me back in January to recommend switching from openzwave to Z-Wave JS. Michael Stegeman (WebThings emeritus module owner) agreed that it looked promising and would save us a lot of headaches.
The WebThings Z-Wave adapter module is currently lacking an owner, but Dave Hylands (the previous module owner) has offered to provide code reviews if anyone wants to work on it.
Alternatively if anyone wants to try creating a replacement Z-Wave adapter in JavaScript then we could consider switching to it as the default once it becomes more mature.
Regarding WebThings being on “life support”, please see this post regarding the future of the project.