Steam has begun displaying a new notice in its shopping cart, explicitly clarifying the nature of the transaction: “A purchase of a digital product grants a license for the product on Steam.” The change is Valve’s way of complying with an incoming California law prohibiting digital marketplaces from implying that customers own the games, movies, ebooks, and other digital content they buy.
Honestly I wouldn’t be shocked if there was some “remote kill” built into those local installers. For all you know it might delete itself on a particular date.