PureOS is described as 'An operating system that respects your rights to privacy, security, and freedom, by design' and is a Linux Distro in the OS & Utilities category. There are more than 50 alternatives to PureOS for a variety of platforms, including Linux, Windows, BSD, Self-Hosted solutions and Mac. The best alternative is Ubuntu, which is both free and Open Source. Other great apps like PureOS are Debian (Free, Open Source), Linux Mint (Free, Open Source), Arch Linux (Free, Open Source) and Android (Free, Open Source).
ReactOS™ is an Open Source effort to develop a quality operating system that is compatible with applications and drivers written for the Microsoft® Windows™ NT family of operating systems (NT4, 2000, XP, 2003, Vista, Seven).
FreeBSD is an advanced operating system for x86 compatible (including Pentium® and Athlon™), amd64 compatible (including Opteron™, Athlon™64, and EM64T), ARM, IA-64, PowerPC, PC-98 and UltraSPARC® architectures.
Zorin OS is a multi-functional operating system designed specifically for Windows users who want to have easy and smooth access to Linux. It is based on Ubuntu which is the most popular Linux operating system in the world.
Red Hat is the leader in development, deployment, and management of Linux and open source solutions for Internet infrastructure - ranging from embedded devices to secure Web servers. Red Hat was founded in 1994 by visionary entrepreneurs Bob Young and Marc Ewing.