Sony recently revealed how the PS4 will allow users to share games with each other, and it’s more permissive than you’d think. This is part of Sony’s attempt to make a comprehensive FAQ for the PS4 prior to its release. Users will be able to link a “primary” console to their PSN account. On that console, every single user will be able to use any PSN games that the primary account downloaded. So say that I download a copy of Super Street Fighter IV . As long as we are playing on my primary console, the game can be played no matter what account is logged in. In addition, all other users that use the console will get whatever benefits your PSN account gives you. So, for example, they will be able to play games online if the primary account has PlayStation Plus.
But what if you aren’t playing on your primary system? Well, that’s simple as well. You can download copies of any game you purchased on anyone else’s PS4 at any time. However, only the account that downloaded the game will be able to play it. Thus, not every account on the console will have access to the game. That being said, two consoles can be signed on to the same account simultaneously, your primary console and one secondary console. So you could, say, share a copy of Street Fighter IV with your friends, but you’d only ever be able to play one at a time.
All of this only applies for digital copies of games. As far as disc games go, go bananas! You can share, swap, trade, sell, and otherwise give away these games however you want. They will not be tied to any account, and you don’t have to be signed on to play them.
Only one primary system can be registered at a time, and primary systems can only be deactivated on the primary system itself. In addition, primary systems must be registered in order to use PS Vita remote play.
Source: Official US PlayStation Site