DRM software provides publishers and retailers with a wide variety of options to set rules. If a retailer runs a subscription service, it could require subscribers to renew their song licenses every month.
A site or music label could also allow consumers to download a song, but only for an extra charge. And an e-publisher could allow you to share a book with a friend by making available a single copy that can be passed along but not copied.
Significant problems could arise, however. One of the biggest: Not all DRM software runs on all players. After all, the companies that write the software are competitors. And for now, they’d rather fight for market share than make life less confusing for consumers.
If for example, you buy a song protected by IBM’s software, it won’t run in Microsoft’s Windows Media Player, which only plays Microsoft-protected files. To listen to the IBM-protected music, you’d have to obtain another player.