You don't need any software. It's a stand alone scale. It can be hooked to your computer if you have a Stamps.com account, but you don't need anything to use it to weigh things except to plug it in to the wall.
That is not what the seller is stating. If you have the Stamps.com software installed on your computer (and have an account with them) you can hook this to your computer and it will communicate with the stamps.com software. If you DON"T have the stamps.com software, you DON'T hook it to your computer and it works like a regular scale.