MacRumors.com

Embedded in one of the configuration files of Panther's Software Update is evidence that Apple has planned for the implementation of a new feature in Software Update: Selling Software. In addition, it appears Apple also plans on offering discounts on the sales to current .Mac subscribers.

The Mac OS X 10.3 (Panther) Software Update's English.lproj Localizable.strings file includes the following messages (which were not present in Mac OS X 10.2):

A 1-Click account is required to purchase software.
To purchase software, you need an Apple account with 1-Click ordering enabled. If you don't have an Apple account, you can create one in just a few minutes by clicking Set Up.

Save ?? with a .Mac membership.
.Mac members enjoy free or discounted pricing on software. Click Set Up to make sure your member name and password are correct, or sign up for a .Mac membership. Click Continue if you don't want a .Mac membership now.

Longstanding rumors have hinted that Apple will be revamping Software Update to allow 3rd party developers to provide their own updates through the Apple utility. It's unclear if purchasable software would be limited to Apple's own selections or opened to 3rd party developers as well.