So you want to learn more?
Here is a set of links you should look at if you are new with OS developement:
I surfed far and wide across the internet for a wide variety of opensource OS projects. The most interesting one is project Oberon (and AOS) -there is a modern implementation is called Bluebottle .
Bluebottle is cool , however , documentation is a pain to find and active oberon compilers for linux do not exist (as far as I know)
So Exolu is my answer: I wanted to create something new.