WordPress Taxonomy Radio Buttons

functions.php

<?php

// limit number of categories a person can have
add_filter('wp_terms_checklist_args', 'digsublime_select_one_category');
function digsublime_select_one_category($args) {
    if (isset($args["taxonomy"]) && $args["taxonomy"] == ("lodge" || "chapter" || "section") ) { //put taxonomies to apply this to in quotes
        $args["walker"] = new Walker_Category_Radios;
        $args["checked_ontop"] = false;
    }
    return $args;
}
class Walker_Category_Radios extends Walker {
    var $tree_type = "category";
    var $db_fields = array ("parent" => "parent", "id" => "term_id");
    function start_lvl(&$output, $depth = 0, $args = array()) {
        $indent = str_repeat("\t", $depth);
        $output .= "$indent<ul class=\"children\">\n";
    }
    function end_lvl(&$output, $depth = 0, $args = array()) {
        $indent = str_repeat("\t", $depth);
        $output .= "$indent</ul>\n";
    }
    function start_el(&$output, $category, $depth, $args, $id = 0) {
        extract($args);
        if (empty($taxonomy)) {
            $taxonomy = "category";
        }
        if ($taxonomy == "category") {
            $name = "post_category";
        } else {
            $name = "tax_input[" . $taxonomy . "]";
        }
        $class = in_array($category->term_id, $popular_cats) ? " class=\"popular-category\"" : "";
        $output .= "\n<li id=\"{$taxonomy}-{$category->term_id}\"$class>" . "<label class=\"selectit\"><input value=\"" . $category->term_id . "\" type=\"radio\" name=\"" . $name . "[]\" id=\"in-" . $taxonomy . "-" . $category->term_id . "\"" . checked(in_array($category->term_id, $selected_cats), TRUE, FALSE) . disabled(empty($args["disabled"]), FALSE, FALSE) . " /> " . esc_html( apply_filters("the_category", $category->name)) . "</label>";
    }
    function end_el(&$output, $category, $depth = 0, $args = array()) {
        $output .= "</li>\n";
    }
}