From Online Manual
The SMF copyright displayed at the bottom of every SMF Forum is there for a reason. You are NOT allowed to modify the copyright notice in any way, shape, or form. An example of an SMF copyright is:
<a href="http://www.simplemachines.org/" title="Simple Machines Forum">Powered by SMF 1.1.5</a> | <a href="http://www.simplemachines.org/about/copyright.php" title="Free Forum Software">SMF © 2006–2008, Simple Machines LLC</a>
The SMF license states:
a. A Modification must not alter or remove any copyright notices in the Software or Package, generated or otherwise.
Failure to comply will result in a reminder, then an official warning, followed by legal actions.
For information on the copyright, click on the second part of the copyright or just go to http://www.simplemachines.org/about/copyright.php.