I'm not a lawyer, but it seems to me that what you are doing is using the sounds provided by the libraries, but are not distributing the libraries themselves. You are allowed to create music using those sounds and do whatever you want to with them. So you are just distributing audio content that uses those sounds (not much different than if you created a song using those sounds). The only difference is that the audio can be sliced and diced by BIAB/RealBand; however, you are not distributing the sound libraries themselves.
But again, I'm not a lawyer. I don't even play one on TV (or even YouTube, for that matter).
