Yes, Guix is initially a clone of Nix and has still remains of shared code (the build daemon).

Differences:

• Guix packages are defined in a Scheme dialect called Guile, a nice minimal functional language
• Guix was created as a GNU project and stresses the importance of free software with strong copyleft
• strong focus on long-term reproducibility and capability of tracking the sources
• everything is built from source
• very good and well organized documentation