Almost all ideas can be traced to something else.

Icons were Dave Smith's invention. He came from SRI, so one could easily find someone there who inspired him.

Apple and Microsoft both made significant contributions and Mac/Windows were in no way a "copy of the Alto." In fact, Star itself was not a copy of the Alto; that was the problem it had to solve! The Alto's programs all had different interfaces.

"Direct manipulation with the mouse" was what wowed Jobs, and what he saw was Smalltalk, which had a different interface than any of the stuff I mentioned.

Interestingly, Bill Atkinson was sure he'd seen something cool at the demo that he liked, so he implemented it. It turned out that he hadn't actually seen it.