You're making an unfair generalisation. I'm not sure if that kind of language is often used in software projects, and this specific project comes from Zed Shaw that is well known for his quite "unique" approach to software projects.

I don't know if you're aware of http://programming-motherfucker.com/ -- again, it's a joke, a parody, and it's funny as jokes and parodies are. But honestly, I don't think anybody will really use that kind of language or attitude in a professional environment.

EDIT: typo