Not on the web site yet, but can be downloaded from their FTP site.
Username: irt
Password: Binoculars (case sensitive)
Folder: /BESX_4.1 SP5 Full/
Subject: BES 4.1.5 has been released
Sorry, wrong folder - the one I gave was for the Exchange (spit) version.
The correct one is /BESD_4.1 SP5 Full/