Even though this is "50% complete", it is fully functional with its own servers. It's just there is definitely going to be more added to this mod over time.
Attempting to describe this mod to someone who knows nothing about Beta is like describing Minecraft to someone who's never played Minecraft before. It's hard because there is so much more to it than what you see at the surface, and the stuff beneath the surface of the game is really what lets the game play on the feels. I could go on, but I would be just repeating the introduction on the front page on the wiki: http://newfrontiercraft.net/thread/51/front-page
The wiki also has the download, how to install, a ton of information on the mod, servers, the discord chat, and all that good jazz.