I think for grep in emacs, the only thing require is the interface:

- result on standard output - path and line numbers on each line

A lot of emacs reliance on other tools follow the same pattern. While the default is posix, it has enough options to twist it to fit whatever OS.

parent is talking about the external dependencies, grep.exe and java and jdtls etc., and in particular how they need to be installed separately from Emacs

Do other editors and IDEs bundle-in these external language servers? I don't think so, unless they are specifically tied to the language like Eclipse or PyCharm