BuddyPress.org

require( ‘./wp-load.php’ );
require( ‘./wp-blog-header.php’ );
require($_SERVER . “/wp-content/plugins/buddypress/bp-themes/bp-default/registration/register.php”);

These are the dependencies for the BP registration process. Once all 3 are loaded, the form will work.

I have a custom BP installation in which I bypass the main BP index.php file and use WPMU and BP functions as I need them.

To get the slugs to work, I change my .htaccess file as such:

RewriteRule . index.php?slug=1 [L,NC,QSA]

and then my index.php as such:

if (isset($_GET)) require( ‘./wp-blog-header.php’ );

In that way, the BP header is only loaded when a slug is used, and I can bypass it otherwise.