you can download them to your phone via: http://www.blackberry.com/instantmessaging 
via BerryReview.com by Ronen Halevy on 5/21/09
Its happened again. Nelson & Felix let me know that the official RIM Google Talk, AOL Instant Messenger, Windows Live Messenger, & Yahoo Instant Messenger clients are now sitting pretty at version 2.1.45 compared to version 2.1.44 that came out not to long ago. No idea what changed so let us know in the comments!
You can pick them up at this link OTA