Compatibility between Nix and Guix

[Daniel Schäfer]

Hi all,

I've been using NixOS for a few years and now I want to try out Guix.
The goal is to see whether there is a benefit to using both and what we can learn from each other.

Last year Ludo wrote:
> > Is compatibility with the nix-daemon a goal of the Guix project?
> 
> I’ve come to the conclusion that it’s not a worthy goal, as in, it would
> cost more than it’s worth.  guix-daemon is already incompatible with
> nix-daemon on a few things, such as the “builtin:download” derivation
> builder.

But the Guix manual at 2.2 [1] says:
> When a working installation of the Nix package manager is available, you can
> instead configure Guix with --disable-daemon. In that case, Nix replaces the
> three dependencies above.
> 
> Guix is compatible with Nix, so it is possible to share the same store between
> both. To do so, you must pass configure not only the same --with-store-dir
> value, but also the same --localstatedir value. The latter is essential because
> it specifies where the database that stores metadata about the store is
> located, among other things. The default values for Nix are
> --with-store-dir=/nix/store and --localstatedir=/nix/var. Note that
> --disable-daemon is not required if your goal is to share the store with Nix. 

How much of that is still true? The daemon is not compatible anymore and
I don't think it is a good idea to have two different daemons share the same store.

Is there still the a possibility to use either Nix on GuixSD or Guix on NixOS
without duplicating the store or running two daemons?
Or e.g. use Nix with Guile?

Cheers,
Daniel

[1] https://guix.gnu.org/manual/en/guix.html#Requirements