I just tried it again. This time, the download proceeded normally. I tried your link and found that it also works, although I stopped the download since I already had the file.
Yesterday, I was using Pale Moon x64 for Windows 25.6.0, but last night it was upgraded to version 25.7.0. User agent string: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:25.7) Gecko/20150824 Firefox/31.9 PaleMoon/25.7.0
Yesterday, the download button went to the download page just for a moment, but immediately redirected to the main piriform.com page.