The Blue Elephant Referee Scheduler is licensed under the terms of the GNU General Public License (GPL). In simple terms, this means that the you are completely free to use, modify and redistribute the program for any purpose. However, if you make modifications to the program, you must publicly publish these modifications freely for others to use (preferably by contributing back to this site). In this way, others can enjoy the same freedom you have been granted to use this software.
Some clarifications: For the purposes of the GPL, deploying of the Blue Elephant Referee Scheduler on a website consitutes distribution of the software, binding you to the terms of the license.
There is some debate as to whether the Apache License is compatible with the GPL. The Blue Elephant Referee Scheduler links with certain Apache-licensed software libraries. For the purposes of the GPL, permission is explicitly granted to link with libraries published by the Apache Software Foundation. Linking with these libraries does not constitue a violation of the license. The full permission is detailed below:
As a special exception, the Contributors give permission to link the code of this program with software libraries published by the Apache Software Foundation, and distribute linked combinations including the two. You must obey the GNU General Public License in all respects for all of the code used other than that published by the Apache Software Foundation. If you modify this project, you may extend this exception to your version of the project, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.