I'm sorry, but that's nonsense. AdGuard doesn't have any scummy stuff like "acceptable ads", they make money by providing a fully functional free ad-blocker and selling a version that has more features. That's as un-scummy as it gets. (I have no relation to them. I use the free version. It does everything I want.)

By the way, you can get the source code at https://github.com/AdguardTeam/AdguardForiOS.

There's also a list of open-source content blockers at https://old.reddit.com/comments/btlwda/, some of them are non-commercial.