sway: wallpaper: Specify license

modules/default.nix

@@ -102,6 +102,7 @@
         pkg: builtins.elem (lib.getName pkg) [
           "corefonts"
           "vista-fonts"
+          "wallpaper-unfree" # defined in users/simon/modules/sway.nix
           "p7zip" # exception: rar source code is not free, but available; p7zip with `enableUnfree` includes it
         ]
       );

users/simon/modules/sway.nix

@@ -4,7 +4,7 @@ let
   solarized = common.colorschemes.solarized;
 
   wallpaper = pkgs.stdenvNoCC.mkDerivation {
-    name = "wallpaper";
+    name = "wallpaper-unfree";
 
     src = pkgs.fetchurl {
       url = "https://i.pximg.net/img-original/img/2013/10/22/04/25/37/39266182_p0.jpg";
@@ -28,6 +28,9 @@ let
     dontUnpack = true;
     dontConfigure = true;
     dontFixup = true;
+
+    # Source: “境目” by 3211 on Pixiv: https://www.pixiv.net/en/artworks/39266182
+    meta.license = lib.licenses.unfree;
   };
 
   cfg = config.wayland.windowManager.sway.config;