macOS grep is from FreeBSD, at least as of macOS Mojave (10.14). (Source code for 10.14 might be at https://opensource.apple.com/source/text_cmds/text_cmds-99/g

macOS grep is from FreeBSD, at least as of macOS Mojave (10.14). (Source code for 10.14 might be at https://opensource.apple.com/source/text_cmds/text_cmds-99/grep/grep.c.auto.html https://opensource.apple.com/source/text_cmds/text_cmds-99/g....) Not sure if it was ever GNU grep. Maybe before the big purge in 2011? IME, most of the basic shell commands are either directly from FreeBSD or a project in the BSD universe. For example tar is from libarchive, a distinct project (see https://github.com/libarchive/libarchive https://github.com/libarchive/libarchive) that DragonflyBSD, FreeBSD, NetBSD, and macOS import and track. (But oddly not OpenBSD, which has evolved the 4.4BSD-Lite implementation.) According to a 2012 accounting at http://meta.ath0.com/2012/02/05/apples-great-gpl-purge/ http://meta.ath0.com/2012/02/05/apples-great-gpl-purge/ (via https://news.ycombinator.com/item?id=3559990 https://news.ycombinator.com/item?id=3559990), macOS was down to 16 GPL packages in macOS 10.12 from 47 in macOS 10.5.