AIM client for BlackBerry made by RIM being replaced by one built by AOL
It is important that if you use the AIM application and want to continue to use it without interruption, you need to install the AOL built software and remove the old software developed by RIM by Friday. To remove the old RIM-built AIM client, you need to go to the sourcelink and follow the instructions at the bottom of he page. Once the old client is deleted, you can install the AOL built software by heading over to BlackBerry AppWorld and look for the app named "AIM" by AOL. The new AIM client will work for those with a BlackBerry device running OS 4.5 or higher.
source: RIM via Crackberry