docs: add GPL license and source headers

DMRProtocol.pas

@@ -1,3 +1,22 @@
+{
+  Copyright (C)
+  2026 - Uladzimir Karpenka, EW8BAK
+
+  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 2
+  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, write to the Free Software
+  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+}
+
 unit DMRProtocol;
 
 {