OSDev.org

I just found this operating system tutorial

http://exposnitc.github.io/Roadmap.html

It seems very detailed, but i don't see any discussions or forums about it.
So what do you guys think about this OS tutorial?

It's not really an OS tutorial. It's the course content for a university in India and it teaches OS concepts through a "fantasy computer" - a simplified machine that exists only as a simulator. I really don't recommend learning about operating systems this way.