BuddyPress.org

1) Use the BP Template Pack plugin:

https://wordpress.org/extend/plugins/bp-template-pack/

Please follow all of the steps involved.

2) Probably possible but will get messy trying to get cookies and login info integrated. You could try using WPMU or wait a few months when WP 3.0 is released and when BP is made compatible with WP v3.0.