> Bootstrap isn't mainstream enough to warrant it's own foundation/organization
What do you mean by "not mainstream enough?" Organizations on Github are simply a convenient place to put one or more projects that are collectively worked on by a group of individuals and do not necessarily have a single core maintainer.
Yeah, that's what a lot of people seem to be missing here: there's mention of an open-source organization on GitHub but no mention that fat and mdo want to start working on Bootstrap full-time and make money off of it.
Sorry, what I meant by "mainstream" is "have enough of a following". You can say a lot of good things about Bootstrap, and to be fair most of them are probably right, but even when you compare to other jQuery libraries/framework it must have... what, maybe 5% of the users? Also, it's a very young project, it's not an established de facto piece of technology like Django is when it comes to Python web frameworks, Rails to Ruby web frameworks, or Apache is to HTTP servers.