The source for the Linux kernel used in Windows Subsystem for Linux 2
Hobby operating system, bootloader, kernel, drivers, C library
Boots into many systems and GRUB2 ones!
freeRTOS for Arduino Uno, Goldilocks 1284p & Mega 2560
A microkernel-based multiserver operating system written from scratch.
amforth is an extendible interpreter on microcontrollers
x86-64 os made in crystal
An operating system written in RTL
My FreeDOS Floppy Disk Distribution
Kestrel is an experimental kernel runs on i386
Operating System in 512bytes.
A new simple operating system