Reddit reviews K-zer Dorm Shelf 3/16-Inch Foam Core, White

Those are 3M Command adhesive strips. They aren't reusable, but they're inexpensive and leave no residue.

I agree that this project isn't so bad. The general idea is non-ridiculous, I don't see a comparable product on the market (though this is somewhat similar), and there's no evidence that the creators have engaged in any sort of wrongdoing.

I'm not sold on the premise that people would want to carry around one of these things in case they need it, but I wouldn't mind having a few in my home. I'd be willing to pay $20 for a three-pack.

Edit: I see that 3M marketed a shelf of its own. It appears to have been discontinued, which suggests a lack of demand. (However, that product didn't fold down.)

Here is the mobile version of your link