The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Defense Language Institute - Foreign Language Center:
Welcome to AISO Library we serve as the academic library for the students, faculty, and staff of the Defense Language Institute Foreign Language Center (DLIFLC). Search for books, DVDs, audiobooks, software and more. We have also implemented the EBSCO Discovery Service that with search Aisos entire collection both online and in print. Weve invested in the latest mobile solution for libraries and well be adding new content over time. I hope you enjoy it as much as we do!