It is tied to your MSDN account and TFS Online (*which supports Git by the way) account. Upon signing in, you have access to all of your company's shared projec

It is tied to your MSDN account and TFS Online (*which supports Git by the way) account. Upon signing in, you have access to all of your company's shared projects and there is no need to enter any serial number(s). Microsoft are trying to move away from boxed software and into software as a service. Linking everything into your MSDN account is one way to "tick" that box. In 2013 at least, there is a "enter serial" button (forget the exact wording) and you can simply grab a ye' olde serial from your MSDN account and plop it in. But doing so breaks TFS Online (since that relies on your Microsoft Account/MSDN Account for permissions to access projects). But if you'd prefer not to use TFS Online then just use GitHub. Visual Studio supports it. Heck GitHub even released a funky extension to make it just that much easier (and that too requires you to login to an account).