BuddyPress.org

I did this on this site, and like this:

function register_user_as_contributor($username) {

global $bp, $wpdb;



$user_id = bp_core_get_userid_from_user_login( $username );



if ( !$user_id )

return false;



$role = maybe_unserialize( get_usermeta( $user_id, $wpdb->base_prefix . '1_capabilities' ) );



if ( is_array($role) )

$role = $role[0];



if ( !$role || '' == $role || 'subscriber' == $role ) {

$role['contributor'] = 1;



update_usermeta( $user_id, $wpdb->base_prefix . '1_capabilities', $role );

update_usermeta( $user_id, 'primary_blog', 1 );

update_usermeta( $user_id, 'source_domain', 'buddypress.org' );

}

}

add_action( 'wp_login', 'register_user_as_contributor' );

I’m sure there is another action you can use so it doesn’t run on every login, but this works.