Add exception to the GPL

LICENSE.md

@@ -659,3 +659,23 @@ specific requirements.
 if any, to sign a "copyright disclaimer" for the program, if necessary.
 For more information on this, and how to apply and follow the GNU AGPL, see
 <https://www.gnu.org/licenses/>.
+
+"ESSENTIAL AND MINECRAFT" LINKING EXCEPTION TO THE GPL
+
+Linking this mod statically or dynamically with other modules is making a
+combined work based on this mod. Thus, the terms and conditions of the GNU
+General Public License cover the whole combination.
+
+In addition, as a special exception, the copyright holders of this mod give you
+permission to combine this mod with free software programs or libraries that
+are released under the GNU LGPL, with code included in the standard release
+of Minecraft under All Rights Reserved, and/or with code included in the standard
+release of Essential under All Rights Reserved (or modified versions of such code, 
+with unchanged license). You may copy and distribute such a system following the
+terms of the GNU GPL for this mod and the licenses of the other code concerned.
+
+Note that people who make modified versions of this mod are not obligated to
+grant this special exception for their modified versions; it is their choice
+whether to do so. The GNU General Public License gives permission to release a
+modified version without this exception; this exception also makes it possible
+to release a modified version which carries forward this exception.