This is how Wordpress's site tells you to get rid of it:
As long as people use these themes, this practice will continue. It's basic economics.
If you can't decode the footer, try this:
In your index.php find the line that says
<?php get_footer(); ?>
Above and below it place some marker text like this
<!-- Evil Footer Devil FOUND -->
<?php get_footer(); ?>
<!-- Evil Footer Devil BEGONE --> Now visit your blog, view source, and copy the HTML from between the two markers. Rename your footer.php and make a new copy with that HTML code.
Change it to your hearts content. Remember to insert the <?php wp_footer(); ?> before </body> tag.
Keep in mind that if your theme's license for use doe not permit this, then don't do it. If that's the case follow MichaelH's advice and get a friendly theme.
Code:
http://codex.wordpress.org/FAQ_Layout_and_Design#How_to_get_rid_of_encoding_in_a_theme.27s_footer.3F