If you want to author DVD or Blu-ray off the timeline in EDIUS 11 you need to buy this add-on as it is no longer included as default. This add-on is no use without EDIUS 11.
If you have EDIUS 9 you can keep this installed on an EDIUS 11 computer and author DVD and Blu-ray using EDIUS 9. You would need to export an AVI from the EDIUS 11 timeline, add chapters and menus in EDIUS 9 then export. The advantage of buying this add-on is that you can author directly off the timeline in EDIUS 11.
The DVD/Blu-ray authoring is exactly the same with EDIUS 11 as it is with EDIUS 9.