[Groxx]

Just as a small note, as far as I can tell the PPC -> x86 version of Rosetta was at least partly licensed from "Transitive Corporation" by Apple, not entirely in-house: https://en.wikipedia.org/wiki/QuickTransit . I have no idea about Rosetta2 though.

[jibcage]

Transitive was acquired by Apple, I imagine Rosetta 2 was the product of many of the same engineers.

[lukeh]

Transitive was acquired by IBM, not Apple. I believe some engineers ended up at Apple though.