Add metabox to WordPress taxonomies via https://github.com/jaredatch/Custom-Metaboxes-and-Fields-for-WordPress

gistfile1.php

<?php

	// Add for Taxonomies
	function wsm_add_for_taxonomies( $display, $meta_box, $taxonomy ) {
		if ( 'taxonomy' !== $meta_box['show_on']['key'] )
			return $display;

		// Get the post's ID so we can see if it has ancestors					
		if( isset( $_GET['post'] ) ) $post_id = $_GET['post'];
		elseif( isset( $_POST['post_ID'] ) ) $post_id = $_POST['post_ID'];
		if( !isset( $post_id ) )
			return false;

		// If the post is a taxonomy, show the box
		$tax = get_term( $post_id, $taxonomy );
		$slug = $term->slug;
		if( '' != $slug ) 
			return true;
		// Otherwise, it's not taxonomy, so don't show it
		else
			return false;
	}
add_filter( 'cmb_show_on', array( &$this, 'wsm_add_for_taxonomies' ), 10, 2 );