NoChain has existed for a while now, but wasn't originally public. Now it is, with better hardware and a fresh world. The concept is very simple: Pure vanilla, pure freedom. The only "non-vanilla" feature is /sit. Only case where there's any admin involvement is when lag machines are created.
Whether you're playing vanilla, a hacked client, or whatever else, you're free to do so and to do whatever you want (except for lag machines, as I said). Additionally, the world will not be reset, ever.
The IP is: having-weather.joinmc.link
The IP looks strange because the server uses a proxy to allow player connections. It's more secure this way.