Reply To: bbp_setup_current_user was called incorrectly.
As you no doubt already know, this is just a warning message, and bbpress say it is an issue with wordpress, and are waiting for wordpress to fix. Also as you know (but for others reading this), turning off debug fixes this.
If you want it to disappear whilst you are developing (and so need debug on), then go to
wp-content/plugins/bbpress/includes/core/sub-actions.php
and comment out/change line 147
_doing_it_wrong( __FUNCTION__, __( 'The current user is being initialized without using $wp->init().', 'bbpress' ), '2.3' );
to
//_doing_it_wrong( __FUNCTION__, __( 'The current user is being initialized without using $wp->init().', 'bbpress' ), '2.3' );
and change back after developing as well as turning debug off for the production environment
