Allow only specific usernames

Hi, I am trying to set up a website for my minecraft server. I want to set up the buddypress registration to only allow users to register if their username reads as a premium account on the minecraft.net server. I found a plugin that was meant to do that, but it hasn’t been updated for a long time, and it no longer works. I have been trying to alter the plugin, but so far, it hasn’t shown any results. As far as I can tell, the plugin is not blocking users, and that is all. Could someone tell me if I have done something wrong?
I have changed the code a lot from the original, but I don’t think that I have damaged anything, let me know if you need the original, and I will post it.

EDIT: It turns out that I did damage some of the code, I was getting a very small error on the wordpress plugin page, I fixed that, and upaded the code below.

Here is the plugin’s code:

<?php
/*
   Plugin Name: Minecraft Validator
   Description: Simple plugin to verify new WordPress accounts against the Minecraft user database. If the username doesn't show up as a valid Minecraft player, it won't let them register.
   Version: 1.4
   Author: Ghost1227
   Author URI: http://www.ghost1227.com
*/

/* Run activation hook when plugin is activated */
register_activation_hook(__FILE__, 'get_wp_version');

/* Rewrite registration form */
function mcv_registration_form() {
	wp_enqueue_script( 'login_form', plugins_url() . '/minecraft-validator/usernamerewrite.js', array('jquery'), false, false );
}
add_action('login_head', 'mcv_registration_form');

/* Get WordPress version */
function get_wp_version() {
    global $wp_version;
    if ( version_compare ( $wp_version, '3.1', '<')) {
        exit ( "<div style='font-size: 13px; font-family: 'HelveticaNeue-Light', 'Helvetica Neue Light', 'Helvetica Neue', sans-serif;'><strong>Attention:</strong> This plugin will not work with your version of WordPress.</div>" );
    }
}

/* Register actions */
add_action('register_post', 'verify_mc_account', 10, 3);
add_action('admin_menu', 'add_mcval_options');

/* Check account on minecraft.net */
function verify_mc_account($login, $email, $errors) {
	$user_info = get_userdata(1);
	$options = array(
        'timeout' => 5,
    );
    $mcacct = wp_remote_get('http://www.minecraft.net/haspaid.jsp?user='.$user_info->user_login);

    if ( $mcacct == 'false' ) {
        if ( $mcacct == 'false' ) {
            $errors->add('mc_error',__('<strong>ERROR:</strong> Minecraft account is invalid.'));
            return $errors;
        } else {
            $errors->add('mc_error',__('<strong>ERROR:</strong> Unable to contact minecraft.net.'));
            return $errors;
        }
        add_filter('registration_errors', 'verify_mc_account', 10, 3);
    }
}
/* Activation/Deactivation */
function set_mcval_options() {
    add_option('hide_me', 'false');
}

function unset_mcval_options() {
    delete_option('hide_me');
}

register_activation_hook(__FILE__, 'set_mcval_options');
register_deactivation_hook(__FILE__, 'unset_mcval_options');

/* Add admin menu */
function add_mcval_options() {
    if ( get_option('hide_me') != "true" ) {
        add_options_page('Minecraft Validator Options', 'Minecraft Validator', 8, 'mcval-options', 'mcval_options');
    }
}

/* Display options page */
function mcval_options() {

    ?>

    <div class="wrap">
        <h2>Minecraft Validator</h2>

    <?php
        if ( $_REQUEST['submit'] ) {
            update_mcval_options();
            ?>
                <script type="text/javascript">
                <!--
                    window.location = <?php echo "'options-general.php'"; ?>
                //-->
                </script>
            <?php
        }
        print_mcval_form();
    ?>

    </div>

<?php }

function update_mcval_options() {
    update_option( 'hide_me', 'true' );
}

function print_mcval_form() {
    ?>

<?php }