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 EquationPlotter:
The EquationPlotter application provides an insightful exploration of some of the basic properties of functions. Linear, quadratic cubic and sinusoidal functions are explored in this first version of the app. The app is NOT a graphing calculator, but rather a tool to dynamically explore and understand the behavior of these functions. By using sliders to manipulate different parameters, the user will be able to interact with the functions and their corresponding graphical representations.
