While Steam users aren't allowed to resell their digital games, it's been spotted in the code of the latest beta update that digital gaming service may soon get the ability to share games with friends, allowing users to give access to certain games to friends if they aren't currently playing them.
The lines of code refer to the feature as a "shared game library," and while it doesn't detail how exactly you'll be able to share a game, it suggests that you can share a game if you're not playing it. For instance, if you share a game with a friend and they're currently playing it, you won't be able to play it yourself until they quit the game.
Right now in Steam, you aren't able to do anything with your games other than play them yourself. You can't trade them, sell them, or return them. Once you buy a game, it's yours forever. However, with this new feature, you'll be able to at least share them with friends if you're feeling rather generous.
Of course, it'll be interesting as to how this will be implemented, and what game publishers will think about the idea. We can't be sure that publishers will be totally on board with it at first, but we could see them eventually come around to the idea. It's possible that sharing games with friends will make them want to buy the game for themselves, sort of like a try-before-you-buy type of thing.
However, this is simply just a beta that the code was found it. Beta versions of software have features that sometimes don't make it in the final release, so it's possible that Valve may like the idea, but if they can't get publishers on board, then sharing games with friends on Steam may never see the light of day.
SOURCE: NeoGAF Forums