The Wall Street Journal:
Mr. Murphy said he... plans to implement an option within (Crystal) whereby “acceptable” ads will be displayed to users. The feature will be switched on by default, Mr. Murphy said, and he will receive a flat monthly fee... in return.
Definitely seems like a shady business to be in. I'm starting to understand more why it wouldn't feel good to have built one of these apps.
I think it's funny that the two ad blocking apps I downloaded the day iOS 9 came out were Crystal and Peace. I sure can pick 'em.