The Tweety license comment should be the header comment of all class files. To have Eclipse add it automatically to newly created files, go to Window -> Preferences -> Java -> Code Style -> Code Templates. In the "Comments" tab, edit the "Files" pattern to contain the following:
/*
* This file is part of "TweetyProject", a collection of Java libraries for
* logical aspects of artificial intelligence and knowledge representation.
*
* TweetyProject is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 3 as
* published by the Free Software Foundation.
*
* 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright CURRENT_YEAR The TweetyProject Team <http://tweetyproject.org/contact/>
*/
CURRENT_YEAR should be replaced by the current year. Afterwards, check the "Automatically add comments for new methods, types, modules, packages and files" checkmark.
If errors occur, try right-clicking on a library in your package explorer and choosing: "Maven -> Update Project...".