If you mean those released after Niflheim, the invitation codes in Wizardess Heart, Blood in Roses, and The Niflheim do not do give you referral rewards. If you remember from Niflheim, there was never an option to input such codes during the tutorial, and there is no opportunity on the app itself. All of the newest SWD apps with this particular format have eliminated the use of the invite code other than the ability to FIND friends for the "social" greeting portion.

There is an outgoing link to the app store, but their intention is for players to type a review and rate their app if you want others to simply see your code.