Watch out! This tutorial is over 8 years old. Please keep this in mind as some code snippets provided may no longer work or need modification to work on current systems.
Change the message that appears in the admin footer, why not give yourself a credit for the theme?
// Customise the footer in admin area
function itlc_footer_admin () {
echo 'Theme designed and developed by <a href="#" target="_blank">YourNameHere</a> and powered by <a href="http://wordpress.org" target="_blank">WordPress</a>.';
}
add_filter('admin_footer_text', 'itlc_footer_admin');