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 Vicinno Soft:
Vicinno 15C scientific calculator is the most accurate and precise emulator of the world-renowned HP 15C RPN high-end scientific programmable calculator available for Mac. We use the identical mathematics and calculations with the original to give you reliable, bug-free, precision and accuracy. It can perform numerical integration and solve the roots of equations in addition to supporting complex numbers and matrix calculations.Features include: Root finder Numeric integration Complex numbers Matrix operations Hyperbolic and inverse hyperbolic trig functions Probability (combinations and permutations) Factorial, % change, and absolute value Random number generator RPN entry Programmable MoreSupport:Feel free to contact us if you need any support by visiting www.vicinno.com or simply email us at firstname.lastname@example.org.