Here you will find code from the introduction to the book, including code from a sign help up in a protest in India, the Women in Github webpage, and Votebox electronic voting software. The code for the Climategate software is part of the Chapter 4 discussion.
And here is a link to the original Critical Code Studies manifesto published in electronic book review. It has been revised and extended in the book.
You can read the introductory chapter as a sample of the book.