Aurora HDR 2018 is available until March 31st for download from this link
It is a promotional offer in attempt to get you to buy the 2019 version. However this is a FULL version of the 2018 software
Follow the instructions on the link and you will get an email with a download link and activation code.
Once you have installed the software just activate it with the code
be aware that this is a promotion by the manufacturer, and you most probably will get marketing emails from them