How to import

To import with flakes use

inputs = {
  polymc.url = "github:PolyMC/PolyMC";
};

...

nixpkgs.overlays = [ inputs.polymc.overlay.${system} ]; ## Within configuration.nix

To import without flakes use channels:

sudo -i nix-channel --add https://github.com/PolyMC/PolyMC/archive/master.tar.gz polymc
sudo -i nix-channel --update polymc
nix-env -iA polymc

or alternatively you can use

nixpkgs.overlays = [
  (import (builtins.fetchTarball "https://github.com/lourkeur/PolyMC/archive/develop.tar.gz")).overlay
]