MEDDAC is the seeding point for designing a new approach to Operating System design itself. It is an Open Source project with roots in mainframe design and development the author began in 1979. Monitor Editor Disassembler Decompiler Assembler Compiler
Horizon is a research project aimed at developing a 32-bit Operating System for the Intel architecture. It's written in C and assembler (GAS syntax) and one of its main characteristics is full network integration.