Simplified XenForo API made specifically for grabbing the latest version of a resource.

version.php

<?php
$resource = XenAPI::getResource(1);

echo json_encode($resource);

class XenAPI
{
    private static $isset = FALSE;
    private static $xf_dir;
    private static $modules = array();

    private static function checkInstallation()
    {
        if (self::$isset !== TRUE) {
            self::$xf_dir = dirname(__FILE__);
            require_once(self::getRootDirectory() . '/library/XenForo/Autoloader.php');
            XenForo_Autoloader::getInstance()->setupAutoloader(self::getLibraryDirectory());
            XenForo_Application::initialize(self::getLibraryDirectory(), self::getRootDirectory());
            XenForo_Application::set('page_start_time', microtime(TRUE));
            $deps = new XenForo_Dependencies_Public();
            $deps->preLoadData();
            self::$modules['resource'] = XenForo_Model::create('XenResource_Model_Resource');
            self::$modules['resource_version'] = XenForo_Model::create('XenResource_Model_Version');
            self::$modules['attachment'] = XenForo_Model::create('XenForo_Model_Attachment');
            self::$isset = TRUE;
        }
    }

    private static function getRootDirectory()
    {
        return self::$xf_dir;
    }

    private static function getLibraryDirectory()
    {
        return self::getRootDirectory() . '/library';
    }

    public static function getResource($resource_id, $fetch_options = array())
    {
        self::checkInstallation();
        $resource = self::getModule('resource')->getResourceById($resource_id, $fetch_options);
        $resource_version = self::getModule('resource_version')->getVersionById(
            $resource['current_version_id'], 
            array('join' => XenResource_Model_Version::FETCH_FILE)
        );
        $resource['current_version_string'] = $resource_version['version_string'];
        if ($resource['is_fileless'] === 0) {
            $attachment_id = $resource_version['attachment_id'];
            $attachment = $this->getModels()->getModel('attachment')->getAttachmentById($attachment_id);
            $resource['current_file_hash'] = $attachment['file_hash'];
        }
        return $resource;
    }

    private static function getModule($module)
    {
        return self::$modules[$module];
    }
}
?>