Is Github.com source code open source? [closed]

... or the shoemaker's children go barefoot?

I would like to fix some styling & have an idea for the feature (and a lot of free time) but I cannot find any github.com page on github.com.

GitHub isn't open-source, but you can apply your ideas on an (open-source) GitHub-look-alike:

GitLab

A ruby application with its source code here).
They accept suggestions and pull requests

gogs.io (less active than gitea)

Update 2015: you also have other GitHub-look-alike in Go:

gitea.com

GitBLit

I was wondering the same thing!

They seem to have some open source code but not the entire code base.

check it out here: https://github.com/github