I can see the same on some of the links. I can't quite explain what it might be, but if you copy the link directly and paste it in your browser address bar, it starts downloading for me. It might be worth a try for anyone having trouble just clicking the link.
PC:
http://cdnfiles.ootpdevelopments.com...otp21setup.exe
MAC:
http://cdnfiles.ootpdevelopments.com...1Installer.dmg
*edit to clarify: on windows/chrome, if you right click the link, hit "copy link address", and then paste that in a new tab, it should start the download. At least, it did for me.