It should be up to the buyer whether or not they choose to take that risk, not to the seller to paternalistically make that decision for them.

Errr, isn't traditionally the seller that decides, if, when and for how long they want to sell their wares?

But in this case, the buyer already purchased the product.

And lost it, and was looking for a replacement.

> I wanted to install Aperture on a new laptop; since it's been pulled from the App store I couldn't find it anymore i.e., bought a license and installed the application, but wasn’t given a legal way to do the exact same thing on another computer—one of the rights Apple grants to users of the App Store; nothing lost, no replacement needed

Not quite the same. At least you'd have the option to run the old software in a virtual machine or on an old spare piece of hardware.