It's open source software so it can (given enough time and motivation) be ported to whatever platform you wanted. Because of this I think there's a few other OS

It's open source software so it can (given enough time and motivation) be ported to whatever platform you wanted. Because of this I think there's a few other OSs / distro forks that also use pacman. But primarily, `pacman` is developed by ArchLinux maintainers for ArchLinux.