Darling is a translation layer for running macOS (10.15; command-line) apps on Linux. It’s built on Darwin and is similar to WINE.
Might be interesting if, say, you want to look into maybe supporting your command-line app on macOS without having to pay Apple a few grand every-so-many years or mess with setting up a virtual machine for an operating system that doesn’t want to run on any device Tim Cook doesn’t personally profit from.