It's the official GNU extension language, so it's fairly widely used in the GNU world I think. It's also the language of the init system/service manager on Gui

It's the official GNU extension language, so it's fairly widely used in the GNU world I think. It's also the language of the init system/service manager on GuixSD (the full OS distribution based on Guix), GNU Shepherd (a.k.a. dmd), and IIRC their initrd runs a Guile program instead of a shell script.