 It is compatible because it can be re-licensed under other licenses.The MIT license is compatible with many copyleft licenses, such as the GNU General Public License (GPL); MIT licensed software can be re-licensed as GPL software, and integrated with other GPL software, but not the other way around.The MIT license also permits reuse within proprietary software, provided that either all copies of the licensed software include a copy of the MIT License terms and the copyright notice, or the software is re-licensed to remove this requirement.