"Mainline" is the official new name of the original BT client made by Bram Cohen. It does include many of the features found in uTorrent. At this time, there are no plans to merge the 2 clients {Mainline and uTorrent}.
Mainline will be used by the Movie Industry as part of their attempt to get into the direct download market. So, YES, Mainline will report directly to the MPAA, at least while you are doing a "direct" download from a movie studio.
Azureus also has a separate client "Vuze" that will be used by the movie industry, for the same reason as with Mainline.
So, to recap;
Avoid Mainline and Vuze, as if your life depended on it.
