you need the original assets. KeeperFX replaces the executable and doesn’t ship with the original assets, because it’s not theirs to distribute. The question is

you need the original assets. KeeperFX replaces the executable and doesn’t ship with the original assets, because it’s not theirs to distribute. The question is simply how you obtain the assets. You don’t have a purchase/download option available to only acquire the assets, so you’ll inevitably purchase & download original assets + original executable, discard the original executable and use original assets + keeperfx executable. Or you’ll acquire the original assets alone through nefarious means and can then just use it with the keeperfx executable. Technically I don’t think you can be requested to provide proof of ownership, but keeperfx can definitely be taken down for distribution of assets they don’t own. So the acquisition of those assets falls on you to resolve and is outside their concern. They can only recommend you to purchase the rights to those assets from the proper rights-holders.