Prominent components of the GNU system include the GNU Compiler Collection (GCC), the GNU C Library (glibc), the GNU Emacs text editor, and the GNOME desktop environment.
Many GNU programs have been ported to a multitude of other operating systems, including various proprietary platforms such as Microsoft Windows and Mac OS X. They are often installed on proprietary Unix systems as replacements for the proprietary utilities originally included. However, this practice is controversial: these GNU component programs were developed with the goal of replacing entire proprietary UNIX systems with free software, not enhancing these systems.
Many GNU programs have been tested against their proprietary Unix counterparts and shown as being more reliable.
As of 2007, there are a total of 319 GNU packages hosted on the official GNU development site.
Although the official kernel of GNU is the GNU Hurd microkernel, variants using other kernels have been developed. Usage with the Linux kernel, a monolithic kernel, is by far the most popular distribution-vector for GNU software, though unlike Hurd, the Linux kernel itself is not part of the GNU Project, though the GNU Project has endorsed variants using the Linux kernel, such as gNewSense.
Other GNU variants which do not use the Hurd as a kernel include Nexenta OS (GNU plus the kernel of OpenSolaris) and GNU-Darwin. Debian GNU/kFreeBSD and Debian GNU/NetBSD from Debian bring the early plan of GNU on a BSD kernel full circle. (The Debian project distributes GNU itself as Debian GNU/Hurd.)