I've found this, I havent did it myself but it tells you how to do it:
Short Explanation: A game is bought. Four people and the original purchaser use this same ID to download the game to their PS3's. You keep the ID on your system for as long as you want the game.
*If you will be hosting a game share*
You can use your own PSN ID if you have already purchased games and want to share them for money/GTD. For most sharing it's a pretty good idea to make a new PSN ID.
* Go to the left side of the XMB and hit "Create New User". Make it any name you want.
* Go to the right side of XMB. You will only have 1 option, to make a PSN ID. You will put in an E-mail address. Either put in one of your own, or make a new spam account on Yahoo Mail(recommended).
* Your new PSN ID is ready to be used. Go through the normal steps for buying a PSN game.
* After buying and downloading your new purchase go to the right side of XMB to account management. Select Account Management again.
* Here, go to "Edit Billing Info" and remove all information. Then go to "Edit Account Info" and remove all that information. This is so that no one can get on this account and purchase other software on your dime. Use this if you don't personally know the people in your group.
* Send username/password out to the people who have payed you for their portion of the game.
*Now when the buyer logs in on your account, receive the GTD
* It's likely that each person has to download the game one at a time, but this is not tested.
* KEEP THIS PSN ID ON YOUR SYSTEM OR ELSE YOU CAN'T USE THE GAME ANYMORE
*If you are purchasing the game through a sharing host*
* Go to the left side of the XMB and hit "Create New User". Make it any name you want.
* Go to the right side of XMB. You will only have 1 option, to make a PSN ID. Select "Use existing account" and put in the info that was sent to you by the person hosting your share.
* Now you should be able to get on the PS Store, and click on "Download List". In this list will be the downloads that have been made on the account. Whatever game has been bought on the account will be right there. Click download, and you're set.
* Log off of the ID when you have finished and you can play the game on your regular ID!
* KEEP THIS PSN ID ON YOUR SYSTEM OR ELSE YOU CAN'T USE THE GAME ANYMORE!!!
Logged