The GNU General Public License, written by Richard Stallman of the Free Software Foundation (FSF) for the GNU Project, is one of the widely used free software licenses, which guarantees end users the freedom to run, study, share and modify the software. The GPL is a copyleft license, which means that derivative work can only be distributed under the same license terms. Below are the GPL license in multiple versions:
The Mozilla Public License (MPL) is a free and open source software license developed and maintained by the Mozilla Foundation, a not-for-profit organization that exists to support and collectively lead the open source Mozilla project. The MPL is the license for Mozilla Firefox, Mozilla Thunderbird, and most other Mozilla software, but it has been used by others, such as Adobe to license their Flex product line.
The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT). It puts only very limited restriction on reuse and has. The MIT license permits reuse within proprietary software provided that all copies of the licensed software include a copy of the MIT License terms and the copyright notice. Below is the MIT License: