There is a lot of instruments, that don't need k8s to be scalable and reliable. Starting from stateless services and simple load balancers and ending with actor systems like in Erlang or Akka.
Religious. Open source versions of products that are created/supported by companies providing proprietary versions of the same product have caused me so many problems in the past that now I don't approve this practice.
It should be the same exact copy, or situation turns into "try demo version, buy the full product". At least from my point of view.
I did it mostly by religious reason, but also because everyone writes about Headscale and I didn't want to write about things that everyone already knows.