It depends. Almost all Hollywood DVD’s have CSS copy protection on them. The DVD’s you get from NetFlix also have CSS copy protection. The intention is to deter normal users from making copies. When one tries to copy a DVD with CSS copy protection the software will inform the users that the DVD cannot be copied. But this only applies to reputable software such as NERO, ImgBurn, etc. Since the algorithm of CSS has long been cracked, there are hacker software that can make DVD copies with just few mouse clicks.
So CSS copy protection is meant for the gentlemen and not for the villains. Ask yourself how valuable your content is before making the decision on adding CSS. The cost of having CSS is very minimum; $150 per title if you purchase your DVD replication from New Cyberian. If you are selling your DVD for couple of hundreds dollars, then CSS is worth the money. If you are only selling at $10 to $20, ask one more question whether your prospect buyers will tend to make copies for archiving or distributing. If just for archiving then not having CSS probably will not hurt your sales. Otherwise add it anyway.
If you need to add CSS on your DVD you can just send your master as if there is no need for CSS. New Cyberian is among the very few companies that can add CSS to an already authored DVD. If your current replicator request you to have DDP or DLT then tell them to send the master to New Cyberian instead. We don’t have all these updated requirements.