GNU Hurd
Portability towards other operating systems, such as those derived from BSD, including macOS, is under active development by the Gentoo/Alt project. The Gentoo/FreeBSD project already has a working guide based on FreeSBIE, while Gentoo/NetBSD, Gentoo/OpenBSD and Gentoo/DragonFly are being developed. There is also a project to get Portage working on OpenSolaris. There was an unofficial project to create a Gentoo port to GNU Hurd, but it has been inactive since 2006.