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 The Open University:
Reading, even in the digital age, is probably one of the most important skills that children acquire. It can be an important source of pleasure which also develops vital language and social skills. It is fundamental to most school activities, it can also open up new worlds and give access to the wealth of human knowledge.This app that has been developed by child psychologists and other specialists at The Open University enables young children to take part in fun games which can help develop interests and skills that will be relevant to them when they start to read.