diff --git a/src/Lock-Module-Source.ino b/src/Lock-Module-Source.ino
index e5e64cf..94fc559 100644
--- a/src/Lock-Module-Source.ino
+++ b/src/Lock-Module-Source.ino
@@ -1,3 +1,20 @@
+/*
+Copyright (C) 2024  Riccardo Henning and Philipp Wagner
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
 #include "Arduino.h"
 #include "SoftwareSerial.h"
 #include "DFRobotDFPlayerMini.h"