I don't want a flame about Gates again, but you have to admit the guy is funny sometimes.
About the "sentences", "MS invented the gui" is incredible.
Let's see, without even Googling, there were Douglas Engelbart's early user interface experiments, including the first use of a pointer, then there were also several implementations of Smalltalk which also advanced the OO back-end of GUIs, then the first Macintosh operating systems were based on the Smalltalk interface's appearance (if not its innards) and let's not forget windowing systems like the Symbolics Lisp machines and, ah, lest I forget, X...
Five instances of functional GUIs before MICROS~1 Windows.
About authorship in general, eh, I don't care too much. Well, when I figure something out I like to be credited for it somehow, but I don't hide my process. I don't think I could anyway.