The reason for this is the new trust-system of windows-defender that came with windows 10, it blocks any programms that don't have enough "reputation", which a program gains reputation by getting downloaded by many individuals. Therefor a new program with no reputation gets marked as "Potentially harmfull." To install it anyway, click on "More Info" and then on "Run anyway". Alternatively, you can just download the source-code and compile the program yourself.