The official "top" download was always from BlackBerry.com (now archived). The best current resource is BlackBerry Desktop Software v7.1 (last version supporting the App Loader). Interesting post : Look up "Using BlackBerry Application Loader to unbrick your phone" on forums like CrackBerry.com or XDA Developers — these were the classic "top" guides.

Installs .alx and .cod application files directly from your local hard drive.

The was a core component of the BlackBerry Desktop Software (formerly Desktop Manager) used to install, update, or remove applications on legacy BlackBerry devices.