Most of the "forks" are forks from Twitter employees' personal repos that were created before things got consolidated under Twitter's account. A few aren't and are called out as such. Which ones are missing proper attribution?
I just looked at the list and thought to myself, "Twitter released Mustache.js? They also released webrat? No.. that does not make much sense." and did not realize until I clicked through to those repos and checked to see if it was a fork.
I'm not suggesting Twitter is doing a Bad Thing(tm). I just think we under-appreciate those that create and release open source software and that any sort of nod of the head is a Good Thing(tm).