JanOS is an operating system designed to run on the chipset of mobile phones. It runs without a screen, and allows you to access all phone functionality, from calling to the camera, through JavaScript APIs.

Bitrig is a free, fast, and secure Unix-like Open Source operating system. It is available on current hardware platforms. The source code is freely available under a permissive license.

Manux is a free (libre) Linux-compatible operating system designed to withstand zero-day attacks in userspace.

Ready. Set. Game. Simple and elegant operating system

64bit and 32bit assembly OS.

MenuetOS is an operating system in development for PC, written completely in 64bit assembly language. Features include pre-emptive and real-time multitasking with multiprocessor support and Graphical User Interface.

AstLinux is a "Network Appliance for Communications" open-source x86_64 Linux software distribution. Unified communications including voice, presence and messaging. Network routing, stateful filtering firewall and VPN support. AstLinux's framework allows integrators and developers to deploy solutions that may be remotely monitored, supported and upgraded using an optimized 60 MB compressed image.