Solarus is available in the nixos-unstable and nixpkgs-unstable channels for the Nix package manager (http://nixos.org/nix/). The editor is pending review on the nixpkgs github repository (at the time of writing), and should enter the above channels shortly. They are not present in a release channel for NixOS, but should be available for the next NixOS release.
Editor is now in the github repo.