I'm an Emacs user, and it plays a significant role in my development process. For 42s code I use Emacs to generate code and process that code for different versions of free42 (I use both free42 & a DM42).
All the code is contained in org-mode files in the src directory.
Binary free42 programs are in the bin directory.
Documentation (rendered org-mode files) may be found in the docs directory.
The documentation is also published here: Docs
Have fun!
-mitch