It appears that Twitter is the source for all of these projects, which is not the case. About 14 of the projects are forks of other repositories on GitHub. Many of the project descriptions include references to their parent projects but it would be nice to see them show it is a Twitter fork and not the main repo.
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).