Linux Desktop OS for professionals
freeRTOS for Arduino Uno, Goldilocks 1284p & Mega 2560
C-BIOS is an open source BIOS for MSX computers.
A microkernel-based multiserver operating system written from scratch.
Operating System written in C# and Cosmos
Real-Time Embedded Operating System
My FreeDOS Floppy Disk Distribution
ext2/3/4 library for microcontrollers
Small real time operating system for AVR and ARM microcontrollers
Kestrel is an experimental kernel runs on i386
Neptune is a kernel and operating system for x86 PCs.
A small operating system, compatible with MS-DOS, written in assemly
Custom firmware and IDE for the VEX Cortex Microcontroller
Mayax is a 32-bit hobby OS with windows style GUI.