PureDarwin is described as 'Darwin is the Open Source operating system from Apple that forms the basis for Mac OS X, and PureDarwin is a community project to make Darwin more usable (some people think of it as the informal successor to OpenDarwin' and is an app in the OS & Utilities category. There are more than 100 alternatives to PureDarwin 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 PureDarwin are Linux Mint (Free, Open Source), Manjaro Linux (Free, Open Source), Arch Linux (Free, Open Source) and Fedora (Free, Open Source).
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.
antiX is a fast, lightweight and easy-to-install linux live CD distribution based on MEPIS and Debian's testing branch for Intel/AMD x86-compatible systems. antiX offers users the "Magic of MEPIS" in an environment suitable for old computers.
Sabayon is a Gentoo-based GNU/Linux Operating System designed for speed and ease of use. With the ability to use Gentoos Portage or Sabayons own Entropy system, the ability to compile a program for your needs or simply install a pre-built binary has never been easier.