Great example. I'm told a lot of banking FinTech is emulating ICL George OS inside, for the core registry function which passed audit, so re-implementing risks re-audit which nobody wants to wear. I know from a friend some banks here in OZ pay COBOL programmers to not die, and keep the bits they haven't ported to Java alive across some API I don't want to even dream about. Probably an ethernet emulating an IBM370 protocol which then winds up in a soft-device into some COBOL tape or disk input strategy
https://news.ycombinator.com/item?id=9808995