According to the link: BlackBerry Messenger App May Be Coming To Apple, Android Devices

Research In Motion (RIM) plans to develop its BlackBerry Messenger (BBM) app for Google’s Android platform and perhaps even for Apple’s iOS devices, according “multiple trusted sources” who dished to Boy Genius Report.
At the Mobile World Congress last month in Barcelona, BBM was named “App of the Year on the BlackBerry App World Platform.” Were RIM to offer its messaging service across multiple platforms, the company could potentially shake up the mobile messaging landscape. Writes Techland, “By extending the BBM service to iPhone and Android handsets, BlackBerry would be able to leverage functionality that it arguably does better than anyone else–quick, simple group messaging–and potentially get users of these other platforms hooked on it.”
But don’t expect these rumored apps to be as robust as the native version. BGR explains.