The link does not work as the creator gives an error message saying it won’t run on this site. I’m pretty sure this might have been a copy protection feature that was implemented by BENO, because he does not like it whenever his programs or creations are distributed to others unless it’s by him.
If you want a working building creator, I have made one on scratch: https://scratch.mit.edu/projects/679413572/. Also beno is making an update to skyscrapersim, which I believe will be released on July 29th.
oh. Maybe it's because your location because it works for me so maybe it's just that you're in a location that doesn't reach that website.