Nix is a new take on package management that is fairly unique. Because of its purity aspects, a lot of issues found in traditional package managers don't appear with Nix.
To find out more about the tool, usage and installation instructions, please read the manual, which is available on the Nix website at https://nixos.org/nix/manual.
Take a look at the Hacking Section of the manual. It helps you to get started with building Nix from source.
Nix is released under the LGPL v2.1