Admin Footer Text Problem

Hello, today,

I first try to install Rebranding WordPress MU plugin, and successful.
then i try to install Admin Footer Text plugin, it give me a message that i need to overwrite the file in server and i clicked yes. then when i refresh the web browser, it gives me an error message:
Fatal error: Cannot redeclare admin_footer_text_site_admin_options_process() (previously declared in /home/content/wp-content/mu-plugins/admin-footer-text.php:44) in /home/content/wp-content/plugins/admin-footer-text.php on line 27

Can you tell me how to solve this problem?