I don't know what this means, so I'm just answering what I'm guessing this means :)
Probably one of the biggest non-OS deployments of Guix is at the institute where I work. We use Guix as a package manager on an HPC cluster. Hundreds of users share the same Guix daemon but each of them can use their own version of Guix with it. They simply invoke "guix pull" to upgrade whenever they feel like it to get a new version of Guix and this affects nobody else.
Users are, of course, not limited to having just one profile. Just like Guix can be used to manage different software environments per user it can just as well be used to manage separate software environments per project. At the institute we do this all the time to create separate environments for independent projects that each have their own upgrade schedule.
We're using Linux libre by default. Guix runs as a package manager on a Hurd system (such as Debian GNU/Hurd) and Guix has packages for building Hurd servers as well, so a Guix System that uses the Hurd instead of Linux libre is close to being ready. Most of this work was done by a very dedicated student who did this as part of GSoC (twice) and who continued to fix problems afterward.
Not all features of Guix will work on a Hurd system; Linux-style containers obviously only work on Linux --- the Hurd has much prettier support for container features, including unprivileged file system virtualization (something I hate to miss on Linux).
The biggest problem with Guix + Hurd is that we aren't yet building packages for the Hurd on our build farms, so no binaries are available. This means there are only very few people who would be willing to use this and report bugs or contribute fixes. I'm planning to attach some Debian GNU/Hurd VMs to the build farm within the next few weeks so that this obstacle is removed. Many of the Guix developers are Hurd enthusiasts (myself included), so I hope now some of us can close the gaps that prevent us from having a native Guix + Hurd GNU system.
> third party channels with non-free software
As one of the maintainers of Guix I'd rather not share links to channels providing non-free software. I also sincerely hope that people will put their time into improving free software than to develop workarounds to allow them to keep software alive that does not respect their freedom and thus harms our communities. That said, there are countless repositories on popular hosting sites that provide package definitions of varying quality for non-free software (also of varying quality :)) --- some of them are also used in HPC deployments.