GNU

Some key points:

GNU is a recursive acronym for "GNU's Not Unix!"
GNU's design is Unix-like, but differs from Unix by being free software and containing no Unix code.
The "free software" concept originated from the GNU project.
Most of GNU is licensed under the General Public License (GPL).

GNU Bash shell (Bash)

GNU C library (glibc)

The GNU C Library.

GNU Compiler Collection (GCC)

For building C / C++.

GNU Core Utilities (coreutils)

The GNU Core Utilities or coreutils is a package of GNU software containing implementations for many of the basic tools, such as cat, ls, and rm.

On mac:

$ brew install coreutils ed findutils gawk gnu-sed gnu-tar grep make

GNU Debugger (GDB)

A portable debugger.

GNU Binary Utilities (binutils)

A set of programming tools for creating and managing binary programs, object files, libraries, profile data, and assembly source code.

GNOME

GIMP: GNU Image Manipulation Program

A free and open-source raster graphics editor.

https://www.gimp.org/

Packages and Binraries

coreutils: [, b2sum, base32, base64, basename, basenc, cat, chcon, chgrp, chmod, chown, chroot, cksum, comm, cp, csplit, cut, date, dd, df, dir, dircolors, dirname, du, echo, env, expand, expr, factor, false, fmt, fold, groups, head, hostid, id, install, join, kill, link, ln, logname, ls, md5sum, mkdir, mkfifo, mknod, mktemp, mv, nice, nl, nohup, nproc, numfmt, od, paste, pathchk, pinky, pr, printenv, printf, ptx, pwd, readlink, realpath, rm, rmdir, runcon, seq, sha1sum, sha224sum, sha256sum, sha384sum, sha512sum, shred, shuf, sleep, sort, split, stat, stdbuf, stty, sum, sync, tac, tail, tee, test, timeout, touch, tr, true, truncate, tsort, tty, uname, unexpand, uniq, unlink, uptime, users, vdir, wc, who, whoami, yes
binutils: ld (the GNU linker), as (the GNU assembler), gold (a new, faster, ELF only linker), gprof (profiler), nm (list symbols exported by object file) etc.
ed: ed, red
gawk: awk
grep: egrep, fgrep, grep
gnu-sed: sed
gnu-tar: tar
make: make
findutils: find, locate, updatedb, xargs