Taxonomy as checkboxes

So I’m trying to get WordPress to display the categories as a series of select boxes in a custom meta box and am using some examples from this tutorial, but when I go to save the selection it generates additional categories in the form of the intended selections ID. It also fails to save more than one selection.

    <?php


    // Add the Meta Box
    function add_custom_meta_box() {
        add_meta_box(
            'custom_meta_box', // $id
            'Custom Meta Box', // $title 
            'show_custom_meta_box', // $callback
            'products', // $page
            'normal', // $context
            'high'); // $priority
    }
    add_action('add_meta_boxes', 'add_custom_meta_box');




      // Field Array
      $prefix = 'custom_';
      $custom_meta_fields = array(
        array(
            'label' => 'Category',
            'id'    => 'category',
            'type'  => 'tax_checkbox'
        ) );



      // The Callback
      function show_custom_meta_box() {
      global $custom_meta_fields, $post;
      // Use nonce for verification
      echo '<input type="hidden" name="custom_meta_box_nonce" value="'.wp_create_nonce(basename(__FILE__)).'" />';

        // Begin the field table and loop
        echo '<table class="form-table">';
        foreach ($custom_meta_fields as $field) {
            // get value of this field if it exists for this post
            $meta = get_post_meta($post->ID, $field['id'], true);
            // begin a table row with
            echo '<tr>
                    <th><label for="'.$field['id'].'">'.$field['label'].'</label></th>
                    <td>';
                    switch($field['type']) {



case 'tax_checkbox':


$terms = get_terms($field['id'],'get=all' );
$post_terms = wp_get_object_terms( get_the_ID(), $field['id'] );

$taxonomy = get_taxonomy( $field['id'] );

$checked = $post_terms ? $taxonomy->hierarchical ? $post_terms[0]->term_id : $post_terms[0]->slug : null;

foreach ( $terms as $term ) {
                                $term_value = $taxonomy->hierarchical ? $term->term_id : $term->slug;
                                echo '<input type="checkbox" value="' . $term_value . '" name="' . $field['id'] . '[]" id="term-' . $term_value . '"' . checked( $checked, $term_value, false ) . ' /> <label for="term-' . $term_value . '">' . $term->name . '</label><br />';
                            }
                            echo '<span class="description">' . $field['desc'] . ' <a href="'.get_bloginfo( 'url' ) . '/wp-admin/edit-tags.php?taxonomy=' . $field['id'] . '&post_type=' . $page . '">Manage ' . $taxonomy->label . '</a></span>';
                        break;





                    } //end switch
            echo '</td></tr>';
        } // end foreach
        echo '</table>'; // end table
      }



    // Save the Data
    function save_custom_meta($post_id) {
        global $custom_meta_fields;

        // verify nonce
        if (!wp_verify_nonce($_POST['custom_meta_box_nonce'], basename(__FILE__))) 
            return $post_id;
        // check autosave
        if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE)
            return $post_id;
        // check permissions
        if ('page' == $_POST['post_type']) {
            if (!current_user_can('edit_page', $post_id))
                return $post_id;
            } elseif (!current_user_can('edit_post', $post_id)) {
                return $post_id;
        }

        // loop through fields and save the data
        foreach ($custom_meta_fields as $field) {


        if($field['type'] == 'tax_select') continue;  


        if( in_array( $field['type'], array( 'tax_checkboxes' ) ) ) {
                        // save taxonomies
                        if ( isset( $_POST[$field['id']] ) ) {
                            $term = $_POST[$field['id']];
                            wp_set_object_terms( $post_id, $term, $field['id'] );
                        }
                    }

                    else {


            $old = get_post_meta($post_id, $field['id'], true);
            $new = $_POST[$field['id']];
            if ($new && $new != $old) {
                update_post_meta($post_id, $field['id'], $new);
            } elseif ('' == $new && $old) {
                delete_post_meta($post_id, $field['id'], $old);
            }
        } } // end foreach

        // save taxonomies
        $post = get_post($post_id);
        $category = $_POST['category'];
        wp_set_object_terms( $post_id, $category, 'category' );
    }
    add_action('save_post', 'save_custom_meta');  



    ?>