Emacs
GNU Emacs as an IDE
Many hackers of yesterday and today runs GNU Emacs for their workflows. Emacs is a kind of tool that respects users freedom and community rights. It is a flexible tool and it sounds like an Operating System because we install packages to extend the limits of Emacs and also we write Emacs Lisp scripts to run interactive actions.
Here you can start with our own copy : GNU Emacs