It might be because GiveAwayOfTheDay is distributing this software, that they are using their own installers which does install some PUP in your system. I ran the installation using UnhackMe's original exe file from their original website and noticed that the installation wizard is different. Also when the original programme is run there is nothing from ESET that stops the installation.
GiveAwayOfTheDay has to earn money from this somehow and I think by using their installer you are downloading some PUP which they are being paid by.
It is really up to you to decide if you trust them enough and if the software is worth it to install it from the website, personally I have skipped this one because I can never justify installing a PUP along side security software, what is the point of security software if it itself contains suspicious files