Rochus and I were arguing about this a couple of weeks ago, and I read through a bunch of historical papers, including Teitelbaum talking about how Smalltalk influenced Interlisp-D and Lampson more or less attributing the GUI to Smalltalk: https://news.ycombinator.com/item?id=49857855

I had no idea about the Interface Builder Lisp history! Thank you for digging that up!