GNU-Darwin is described as 'aims to be the most free software distribution. Our mission is two-fold: Focus on projects that leverage our unique combination of Darwin and GNU, and help users to enjoy the benefits of software freedom' and is an app in the OS & Utilities category. There are more than 100 alternatives to GNU-Darwin for a variety of platforms, including Linux, Self-Hosted solutions, BSD, Windows and Mac. The best alternative is Debian, which is both free and Open Source. Other great apps like GNU-Darwin are Linux Mint (Free, Open Source), Manjaro Linux (Free, Open Source), Arch Linux (Free, Open Source) and Fedora (Free, Open Source).
Chromium OS is an open-source project, used primarily by developers, that aims to build an operating system that provides a fast, simple, and more secure computing experience for people who spend most of their time on the web. Chromium OS and...
BunsenLabs Linux is a distribution offering a light-weight and easily customizable Openbox desktop. The current release is Helium, built on top of Debian (stable). The project is a community continuation of CrunchBang Linux.
MINIX is a POSIX-compliant Unix-like operating system based on a tiny microkernel running in kernel mode with the rest of the operating system running as a number of isolated, protected, processes in user mode.