ReactOS (Source)
ReactOS is an operating system designed to recreate the Windows NT environment (so also the latest systems) as an Open Source project.
Replicant (Source)
Replicant is a fully free Android distribution running on several devices, a free software mobile operating system putting the emphasis on freedom and privacy/security.
Devuan (Source)
Devuan is a fork of the Debian GNU/Linux distribution that started in November 2014. Its stated first goal was to provide a distribution without the systemd init daemon installed by default. The Debian 8 Jessie release had caused polarization among some Debian developers and users, due to the project's adoption of systemd as the default init replacement. The first stable release of Devuan was published on May 25, 2017.