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 Mediated Spaces:
This app lets you collect horseshoe crab species data for use in scientific research. The horseshoe crab, a 300-million-year-old living fossil, is of enormous importance to the drug industry due to its blood, to fisheries for bait, and to migratory shorebirds for its eggs. This Crab App helps you count their abundance, both male and female; counts are usually done around full moons at night, when horseshoe crabs come to lay their eggs in the sand. The app contains information on how to tell the males and females apart. Sign up at the WildLab.org Web site to create your account. This app is a collaboration between the WildLab and the Cornell Cooperative Extension of Suffolk County.