BuddyPress.org

Log into WPMU backend as site admin. Go to Appearances > Plugins. The version of all your plugins, including BuddyPress, is displayed there.

Here’s the versioning info you should see with regards to the BuddyPress plugin:

For BP public release version 1.0 –> 1.0

For BP RC2 –> 1.0-RC2

For BP RC1 –> each individual BP component will show up as it’s own plugin.

As of r1303, which is where RC2 started I believe, BuddyPress was turned into one, big plugin suite.