Currently, Nine Chronicles is comprised of three major projects:
The source code for the game client is located at github.com/planetarium/NineChronicles. This repository houses the entire Unity client of the game, including the interface and graphics resources.
Nine Chronicles in Unity Editor
The whole repository is licensed under GPL-3.0, meaning anyone can fork this repository to make their own versions of Nine Chronicles, as long as they also remain open source. It doesn't even have to be a blockchain game, so imagination is the limit, really.
Much of the game logic actually lives not in the game client, but in the blockchain component of Nine Chronicles. This is because every in-game action needs to be simulate-able and verifiable by other nodes in the network. You can think of the Unity Client as an interface that replays game actions created on the blockchain network.
The blockchain node for Nine Chronicles is nicely nested in a wrapper project called NineChronicles.Headless.
A headless build is a software capable of working on a device without a graphical user interface. NineChronicles.Headless launches the full node of Nine Chronicles without the UI, so you could for instance launch a headless build and write a command-line app to grow your characters on the Nine Chronicles network.