I am not sure that ReacOS is a good example. Quite a big amount of code in ReactOS contains leaked code of Windows (from Windows 2k). Recently I did a research, since I have access to Windows code(code premium subscription), I am able to compare things.
2008/2/23, Fireball wineforum-user@winehq.org:
You could have a look at ReactOS about this (www.reactos.org). But anyway, Wine's way of supporting this will [most probably] be different from reactos' way.