> purist inventors of nixpkgs structured the policy of what must go into nixpkgs to have this rule
No. Both lib.licenses.unfree and lib.licenses.unfreeRedistributable are accepted into Nixpkgs, but the former marker indicates that the developer has declared it illegal to distribute builds so the official binary cache (sorry, “substituter”) does not.
What Homebrew likely does is fetch the upstream binaries from the upstream download server. Nixpkgs does have a policy against that when buildable source code is available, but that’s mostly because the way Nix achieves isolation (both from the host system and between packages) is by placing almost all shared libraries and data files in hash-decorated places that are emphatically different from what an upstream binary expects. On Linux, it’s possible, if very distasteful, to cram that peg into this hole using mount namespaces and bind mounts (see buildFHSEnv et al.); not sure about Darwin, but the general response to asking Nixpkgs maintainers to keep this sort of fragile mess working is, indeed, pretty much exactly “ain’t nobody got time for that”.
No. Both lib.licenses.unfree and lib.licenses.unfreeRedistributable are accepted into Nixpkgs, but the former marker indicates that the developer has declared it illegal to distribute builds so the official binary cache (sorry, “substituter”) does not.
What Homebrew likely does is fetch the upstream binaries from the upstream download server. Nixpkgs does have a policy against that when buildable source code is available, but that’s mostly because the way Nix achieves isolation (both from the host system and between packages) is by placing almost all shared libraries and data files in hash-decorated places that are emphatically different from what an upstream binary expects. On Linux, it’s possible, if very distasteful, to cram that peg into this hole using mount namespaces and bind mounts (see buildFHSEnv et al.); not sure about Darwin, but the general response to asking Nixpkgs maintainers to keep this sort of fragile mess working is, indeed, pretty much exactly “ain’t nobody got time for that”.