That link was known for like a year or even more, and it is not official. All official downloads have links pointed to them from either
https://supertuxkart.net/ (which is an official site) or official github repo (
https://github.com/supertuxkart/stk-code). The only package you could ever pay for was the donator package, which currently does not exist due to absence of future versions of official tracks to include into it, and simple donations which you can find on supertuxkart.net also. You can download source code and compile, or you can download precompiled binaries, all of that will cost nothing for you if you have a device to play.
Back when this link was first discovered, I personally tried to report it, but that led to nothing. If someone has an idea what to do with that, please comment.
Also, it may be not a good idea to ask the question in several places if you already got the answer in one of them.