There once was a time when it was, in practice at least, more difficult and costly to copy videocassette tapes than it was music tapes, compact discs, or computer programs. That, in part, is the justification for how the US Copyright code treats music and computer software differently than, say, movies.

It’s also why you see rental companies, like Blockbuster and Netflix, that specialize in delivering rental videos for limited home usage. Other companies, like Gamefly, specialize in the rental of video games for consoles like the PlayStation 3 and XBox 360. Gamefly can do this because games for consoles, whether cartridge-based or disc-based, don’t qualify as “computer software,” and are thus not under special protection.

And in some states, there are increasing restrictions on how you can sell your used music CDs, for instance.

But as is so often the case in the world of technology, things change rapidly. The advent of the PC and powerful CD and DVD burning technology has made copying DVD movies as easy as copying tracks from a music CD.

Moreover, the PS3 in particular describes itself as a “computer entertainment system,” and comes with a hard drive, to which files can be copied, theoretically easing game load times and storing player profiles and statistics. This raises the question of what truly differentiates a game for the PS3 “computer entertainment system” and a game for a PC. Because of the particularities of copyright law, the former can be rented commercially, while the latter cannot (at least not without direct permission from the copyright holders).

The reason that you can rent games for such console systems is that such a game system is understood to be “a limited purpose computer.” But many PC gaming systems aren’t actually used for anything besides gaming (even though they theoretically could be).

Some commentators are in agreement with the view of Apple’s Steve Jobs: “There’s no mainstream demand for music subscriptions. The music business isn’t built on long-term rentals; it’s built on one hit after another. It’s confectionary. Tunes are addictive for a while and then discarded. It’s like the drug business: Users are always looking for the next hit.”

To the extent that this is even true, it may simply be the result of the different copyright treatment of music, movies, computer software, and video games.