Nix is indeed a replacement for package managers, but the point still stands. Package management and software builds are not completely disjoint - the latter is

Nix is indeed a replacement for package managers, but the point still stands. Package management and software builds are not completely disjoint - the latter is depends quite heavily on the former. Nix itself should work on BSD (I think it's tested on FreeBSD), but Guix is linux-only so far, as it is still in early development. I'm pretty sure Guix intends to be fully portable, even to Hurd in the long term. The ideas behind Nix is platform independent though - there shouldn't be any reason it can't be ported to other platforms. As for building individual software on other platforms - they require different targets. (Or in fact, just an alternative configuration of the same piece of software on the same platform requires a different target). This is intentional though - targets have an identity (a SHA1 of their entire inputs), so any new platform will require a new package. The package configuration format is quite useful in that regard though, as you can derive new package definitions from existing ones, so it should be possible to make partial "generic" configurations, then derive the platform specific targets from them. There's quite a bit of configuration for each platform though, as the dependencies will all have different identities, all the way down to the compiler and the kernel. Another potential option would be to create a template system to automatically generate the Nix configuration for multiple platforms, which would be somewhat similar to what autotools et al are doing today. The difference being, once one person has performed a build and tested it for a platform, anyone else should be able to reproduce it exactly, or to explicitly specify where he wants the target to differ. In effect, Nix removes the "hidden knowledge" that goes into building software by requiring that you specify even the commands you used to perform the build. Of course, Nix isn't a panacea - it introduces a new set of problems, including some social ones. It might take more effort to write portable targets for each platform - but for that trade off you get reliability and simplicity for the users of the software.