SerenityOS

SerenityOS is a graphical Unix-like operating system for desktop computers. The operating system is built from scratch in C++, by the Swede Andreas Kling and a community of developers of all levels. SerenityOS is a love letter to '90s user interfaces with a custom Unix-like core that is built form the ground-up to appeal to today's power-users that want to get things done. The build is monolithic in nature, while allowing anyone to contribute to the core, UI and software for the system.