Copyrights? Copyleft!
Wikipedia articles can be copied and modified by anyone, but there's a catch: All modifications have to be made available under the same conditions, and credit has to be given to the original authors. These are the key terms of the GNU Free Documentation License, under which all article text is licensed. There are various mirrors and forks which use our content, and you can download our entire database to become one of them. However, please only add content which you have created, or which you have been permitted to use under the terms of the GNU Free Documentation License. Everything is copyrighted by default, even if it does not have a notice to that effect.
Read more: Wikipedia:Copyrights