Just reading through the posts:
In my understanding, you would need two licenses to have two seperate working systems.
In the event of a internet failure (or just leaving them off the internet), you can admin-access your server through the TrueNAS UI/CLI (which would defeat the cause of using HexOS, but still works)
(https://hexos.com/blog/the-magic-behind-hexos) - Reliability and Access
Local UI/UX should be coming with the v1.0.