That is because you are trying to download the ad-supported version which is detected as a Potentially Unwanted Program (PUP)
A Potentially Unwanted Program (PUP)
is a very broad threat category which can encompass any number of different programs to include those which are benign as well as problematic. Thus, this type of detection does not always necessarily mean the file is malicious or a bad program. PUPs in and of themselves are not always bad...many are generally known, non-malicious but unwanted software usually containing adware
with other free third-party software as a common practice by legitimate vendors
to include toolbars, add-ons/plug-ins and browser extensions. PUPs are considered unwanted because they can cause undesirable system performance or other problems and are sometimes installed without the user's consent since they are often included when downloading legitimate programs. However, some users may intentionally install
programs with PUP characteristics because they are willing to trade-off the undesirable effects for the benefits
provided by using them.
If you make a small donation, you can download the ad-free version.
More information and Best practices
for downloading software can be found in this topic...