They've always asked that others not host development documentation. Lots of us keep a local copy either for playing around or helping improve them, but you've clearly posted this as a preview of Bootstrap 3 without any permission from Mark.
Btw, I was impressed with what I saw today morning and just wanted to share my impression with other guys.
Which also means there are some informal rules to follow, such as listening to the wishes and requests of those who ultimately maintain the repos.