cc @lheckemann

It’s not a free license, though. https://www.gnu.org/licenses/license-list.html#NASA

I think "free" in licenses.nix means "redistributable" (specifically "Hydra can redistribute") and is not strictly equivalent to "free" of the FSF definition. See #18557 #20256

Unfree package that cannot be redistributed. You can build it yourself, but you cannot redistribute the output of the derivation. Thus it cannot be included in the Nixpkgs channel.
https://nixos.org/nixpkgs/manual/#sec-meta-license

I don’t think that’s right. If that were true, there would be no reason for unfreeRedistributable to exist.

unfreeRedistributable is used for re-distributable binaries, here we also have the source in addition so it is a slightly different case.

In cases where we have access to the source code, but the software isn’t available under a free license, what we have been doing so far (as far as I can tell), is to mark that software as unfree.

Examples:

• https://github.com/NixOS/nixpkgs/blob/46dc76b60b2c2736920fd05b8c6069629a302e41/pkgs/applications/networking/cloudflared/default.nix
• https://github.com/NixOS/nixpkgs/blob/78bc2f9800db2036471963702e038b4f9371593d/pkgs/applications/editors/aseprite/default.nix
• https://github.com/NixOS/nixpkgs/blob/92a047a6c4d46a222e9c323ea85882d0a7a13af8/pkgs/applications/editors/bonzomatic/default.nix
• https://github.com/NixOS/nixpkgs/blob/5051c68c73d6f0fefd0fee25573dbb6c88696e37/pkgs/development/ocaml-modules/cpdf/default.nix
• https://github.com/NixOS/nixpkgs/blob/76c7a8bac083522ea10ba43f699421ca64007708/pkgs/games/xsnow/default.nix

The last ~3 are particularly relevant because they are examples of software where redistribution is explicitly allowed, but the software is still not available under a free license, and so is therefore marked as unfree.

I'm fairly certain that our "free" has historically been roughly what FSF, OSI and DFSG consider free.

We have some vague "free software" description in docs. We might document that more precisely... but it's a bit difficult to describe unless we e.g. write we mean the same as one particular of the organizations above.