BuddyPress.org

Whatever programme you use to look at code (netbeans, dreamweaver,textmate,…) should have a search function that lets you search both files and folders.

There’s no class for the $bp object neither. It’s being created in bp_core_setup_globals(). When you dump $bp onto your screen you’ll see the stdClass, which is the pseudo-class PHP uses for non-initialized objects.