copyright.sh

#!/bin/bash
for i in *.h # or whatever other pattern...
do
  if ! grep -q Copyright $i
  then
    cat copyright.txt $i >$i.new && mv $i.new $i
  fi
done

copyright.txt

// Project Name
// Copyright (C) 2015 Author Name <email>
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
//