This would also affect cc-by-nc-sa-30 and similar licenses. What is our definition of free?

Also see: #20256

I agree with @vyp that FSF definition of "free" is the one that should be used here.

CC BY-NC-SA is less free than vast majority of licenses.unfree packages: if you use the package for commercial purpose (whatever that means), you're breaking the license. See:

https://creativecommons.org/licenses/by-nc-sa/4.0/
https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode

It would be great to adopt a license opt-in mechanism like one seen in Gentoo, licensing issue is more complex than free/unfree, unfortunately.

You can blacklist and whitelist licenses already: https://nixos.org/nixpkgs/manual/#sec-allow-unfree

Yes, I believe all common F/LOSS definitions get broken if you try to restrict use (e.g. to non-commercial).

@vcunat Oh great, haven't seen that! Thanks!

Most unfree packages have generic meta.license = licenses.unfree, but that can be eventually fixed (I already see a few specific unfree licenses in lib/licenses.nix).

@vcunat But there's another problem: currently when one is trying to install an unfree package Nix tells to just add generic allowUnfree = true to config and instead it should ask to whitelist the specific license of the package.

Generally people assume that unfree software doesn't have use restrictions, so e.g. one might mistakenly install CC BY-NC-SA licensed package on a corporate server because allowUnfree = true is set (say, to install oraclejre package).

Perhaps some RFC is needed for defining what "free" and "unfree" means in Nixpkgs?

For this particular case I cannot think of any commonly used definition within the software community that would consider this license free, so personally I'm +1 for merging this PR.