FYI: OS X's grep is FreeBSD's bsdgrep. However, FreeBSD's default grep is still an ancient version of GNU grep (bsdgrep is only available as bsdgrep.).

Also, older versions of OS X used to have GNU grep [1]. So the more likely explanation is Apple's purge of GPL code from OS X. Since later grep versions use GPLv3, GNU grep was a dead end for them.

Unfortunately, FreeBSD's bsdgrep has some very annoying bugs (that are also present in OS X). No one seems to care about them, even when a patch is provided [2].

[1] http://opensource.apple.com/release/mac-os-x-1075/ [2] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=201650