According to the Free Software Foundation , the MIT License is more accurately called the X11 license , since MIT has used many licenses for software and the license was first written for the X Window System . According to the Free Software Foundation , since MIT has used many licenses for software , `` MIT License '' is considered ambiguous , it may accurately refer to the Expat license ( used for the Expat ) or the X11 license ( used for the X Window System by the MIT X Consortium ) .