Valve has announced that Steam Family Sharing is now available to all Steam users. This feature allows you to share your entire game library with friends and family. To start using the feature you first have to authorise shared computers and users. However there are a few things to watch out for such as; VAC cheating bans caused by others, there are some games aren't sharable and DLC isn't lent out to others who own the very same game but not the DLC.
If you are interested in sharing your library of Steam games with family and friends you first have to enable the feature. Open the Steam interface, in the Steam menu click the Settings menu item. In the popup which appears (see below) click Family on the left panel. It is here where you authorise specific computers and users in your circle.
10 devices, 5 users
The newly announced sharing system, previously in Beta, keeps your Steam achievements and game progress safe while other people use your shared computers and devices. Guests also get to keep their own gaming achievements and progress records in the Steam Cloud. There is a limit of ten devices which you can authorise at any one time and up to five accounts can use your game library on any of these shared computers. If you want to share – it's your whole library which is shared.
Other limitations
Valve informs us that some games may not be sharable via Steam Family Sharing because the game in question may "require an additional third-party key, account, or subscription". Two people can't play the same game at the same time; however the owner always has the right to play and the guest will "be given a few minutes to either purchase the game or quit playing," if you want to play.
DLC also gets special treatment; "A guest will have access to the lender's DLC, but only if the guest doesn't also own the base game," writes Valve. Also guests can't just purchase the DLC for games which they don't own. Any of the game's regional restrictions remain for the purpose of lending and borrowing games.
Valve says that if someone cheats or commits fraud using your shared account your sharing privileges may be revoked and the account may also be VAC banned. There is a fully FAQ at the bottom of the Steam Family Sharing page here.
