It's a database table with images with scores that are randomly accessed and presented to the user.
When the user clicks on a photo, + to score, and reload the page with new photos.
All the rest is just candy, really.
Point being either it is trival to create this yourself, or you could google it.
Now, you can approach that by dedicating a lot of time and effort into building something unique, as you would like to do, or you can just realize that the market is pretty bare and launch something that will make some pocket change at worst.
Given that he's considering giving the domain away for free, I simply suggested he do the latter.