The GNU GENERAL PUBLIC LICENSE applies. It specifies COPYING conditions and a NO WARRANTY statement. It is included in the last chapter of this manual, and furthermore as a separate COPYING file in each distribution.
Realize that both my own written code and contributed code by others is owned (via copyright) by Dennis Roddeman. I do this with the explicit intention to make the code freely available under the Gnu Public License. It is setup this way because of logistics issues: legal decisions or modifications to the code would become completely unworkable if there were mixed copyrights. However, I want to credit and give thanks to those people that make the effort of creating code by maintaining a 'thanks to ...' section in the homepage. You can also add 'Programmed by ...' comments in the code that you contribute. If this is unacceptable for you, then don't contribute code.