"So I'm going to be sitting in class for 40 hours a week?"
"No. That would be terribly boring and ineffective. You will spend a little time every day learning through curated tutorials and books, and a lot of the time practicing what you learn. You'll work in pairs and small groups on an exciting integrated curriculum. Your brain will be buzzing as you solve problems, tackle challenges, and build applications until you're confident in your mastery of the skills. If you have an idea for a web app you want to build, then definitely bring it. Also it's important to note that even though class is 40 hours per week, you'll be working more like 70-100 hours per week!"
P.S.- I also attended Dev Bootcamp (with feministy, as it happens). I'd say 70-100 hours per week was accurate for my cohort, although this varies significantly depending on a student's programming background.
Perhaps it's just what you heard people tend to do. I also attended DBC and the "general" hours were very cohort specific; even within each cohort there's a huge variation. However, everyone I met during the bootcamp really enjoyed what we were learning, so naturally that led to long hours if there weren't outside responsibilities.
No you're not. I went to Dev Bootcamp. You're required to be present 40 hours a week, any additional hours are because you choose to do so.