BuddyPress.org

Here’s a different way to do it. It’s not exactly what I want, but it’s a step forward.
For more info, you can see this: https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/move-registration-form-to-home-page
From research, you have to edit slugs to get it to work.
I would be nice to find some examples of editing slugs for bbpress registration form.