The GNU Readline library provides a set of functions for use by applications that allow users to edit command lines as they are typed in. Both Emacs and vi editing modes are available. The Readline library includes additional functions to maintain a list of previously-entered command lines, to recall and perhaps reedit those lines, and perform csh-like history expansion on previous commands.
The history facilites are also placed into a separate library, the History library, as part of the build process. The History library may be used without Readline in applications which desire its capabilities.
Readline is free software, distributed under the terms of the GNU General Public License, version 3. This means that if you want to use Readline in a program that you release or distribute to anyone, the program must be free software and have a GPL-compatible license.
If you would like advice on making your license GPL-compatible, contact email@example.com.