Resource autoloaders are intended to manage namespaced library code that follow Zend Framework coding standard guidelines, but which do not have a 1:1 mapping between the class name and the directory structure. Their primary purpose is to facilitate autoloading application resource code, such as application-specific models, forms, and ACLs.
Resource autoloaders register with the autoloader on instantiation, with the namespace to which they are associated. This allows you to easily namespace code in specific directories, and still reap the benefits of autoloading.