The Application Express Listener Early Adopters Release is available for download at Oracle. Because it’s an early adopters release, it’s not (officially) supported.
The download is available at: http://www.oracle.com/technology/products/database/application_express/html/apex_listener_download.html
The Apex Listener allows developers to use their existing web server (like Tomcat or Weblogic), instead of Oracle HTTP Server/mod_plsql or the XDB HTTP protocol server/embedded PL/SQL gateway. It’s a bit of a preview of things to come in Apex 4.0 later this year (or early next year).
Read the Installation Guide for more information.

