The links are gone, but the files can still be downloaded from Amazon's server:
Windows
macOS
Linux
Kindle Previewer users can find the latest version in the following folders:
Code:
C:\Users\%UserName%\AppData\Local\Amazon\Kindle Previewer 3\lib\fc\bin\kindlegen.exe
Code:
/Applications/Kindle Previewer 3.app/Contents/MacOS/lib/fc/bin/kindlegen