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 Erasmus Universiteit Rotterdam:
The SIN-Online app allows students and employees of the Erasmus University easy access to their relevant timetable, message, folder and grade information.Need to know where and when your next class will be?Check the latest announcements on the course channel? Need to download the latest presentation sheets from the course channel? See your latest grades? It is all possible in a fast and convenient way with the SIN-Online app.Please notice:---------------------The SIN-Online app requires authentication and is therefore only usable by students and employees of the Erasmus University Rotterdam.