[adrianolek]

The "how" link in the top-right corner says:

Your photos are sent to our servers to generate portraits. We won’t use data from your photos for any other purpose and we'll immediately delete them.

So basically you have to trust them.

[giarc]

But then the page has a ton of photos (presumably submitted by users) that I can download. So perhaps the original photo isn't used and deleted, but the generated photo belongs to them.