I've been trying to add the facebook features (Facebook for Blackberry API) to a Blackberry Application but once I add all the files, I get errors from missing libraries in version 4.6.0 (which is the one that I must use as a base and, seems these libraries are only in versions 5.0 and onwards).
That's because Facebook SDK uses BrowserField class that is available from 5.0 OS only. I think it can be rewritten with using RenderingApplication that will allow to use it on lower OSs. But I remember there was performance issue with it on 6+ devices. So it will add more complexity to support two versions.So probably there are more hidden issues. But it's better to ask authors of FB SDK.