Hi Cais,
This is a really cool plugin. I installed it on my test server which uses a separate domain for plugins. This is causing the stylesheets to not be included.
echo '<link type="text/css" rel="stylesheet" href="' . home_url( '/' ) . 'wp-content/plugins/bns-inline-asides/bnsia-style.css" />' . "\n";
could be replaced with:
wp_enqueue_style( 'taxonomy-list-shortcode', plugin_dir_url( __FILE__ ) . '/bnsia-style.css', array(), 'your-version-number-here', 'screen' );
and then hook the function into wp_print_styles
Best,
-Mike