We have all gotten a good look at the new BlackBerry messenger on numerous occasions. Now, you can download an unofficial release (leaked version!) to your device and check it out hands on for yourself. All versions have been posted at BlackBerryOS right down to a compatible version for 83xx devices. The Storm, Tour, Bold and 8900 are all there. Be sure to check it out and remember, these are leaked and NOT official - if you lose all your BBM contacts we cannot be held responsible so back up your data before you try these! Only play around with this if you're comfortable in doing so.
To install via standard method, download the zip to your pc and extract. From there you open Desktop Manager, then Application Loader, browse to the folder containing the file and continue on. If that doesn't work, you can try copying the files to where your OS is installed and overwrite the existing ones. Then run and load Desktop Manager it should now show as 5.0 BBM.
[ Source ]