@jcastaneda
I created the theme on my own with just a bit of help from artisteer.
My problem seems to be in the following line:
echo do_shortcode(theme_get_option('theme_override_default_footer_content') ? theme_get_option('theme_footer_content') : theme_get_array_value($theme_default_options, 'theme_footer_content'));
Basically this line does load the content of my footer_widget.
But I’m not able to change the content in my wordpress-interface.