The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Qbiki Networks:
Keep up with the environmental history community from your phone! EH Mobile is a single portal for news, announcements, blogs, and podcasts about environmental history. By drawing from a wide range of sources, this app will connect you with all of the most up-to-date and relevant information on environmental history research around the world. The simple tab interface connects you immediately to the latest H-Environment announcements, #envhist Twitter posts, NiCHE news, audio and video podcast, blog posts, and new issues of the Environmental History journal.