What is the difference between the GPL and the public domain?

It is a common mistake in perception that Free software licenses such as the GPL are the same as any entity in the public domain. However, there are key differences between Free software licenses and public domain software.

Public domain software is one in which all the developers of the software have agreed explicitly to disclaim all their rights granted to them otherwise by copyright laws. This means that any individual or team cannot assert any rights over the software and everyone is allowed to do whatever they want with it.

GPL license on the other hand, is a copyright license which can be only used under the terms of its license. GPL is, however, unique in the fact that terms of the license are designed to protect the freedom of the end users rather than restrict them from doing things.

Examples of software under the GPL license is the Linux kernel, the core of any Linux based systems such as the Fedora Project or Red Hat Enterprise Linux.