It does not contain ads, you must have stumbled on a name-squatter. The legit one is "net.sourceforge.opencamera". Its description states "Completely free, and no third party ads in the app (I only run third party ads on the website). Open Source."

Battery state is now considered private, personal confidential information also? Hey, my battery is at 78% right now, what are you going to do with that information?

This has nothing to do with poor software design. Any application should be notified when the phone is entering a low power state, or a power saving state, so that the application can disable certain high-power features if the programmers decided to add that feature. Maybe Uber doesn't need a constant GPS feed until you're actually ordering, for example, but it's nice to have that position information if your battery is fine.

The problem is that the rules of English are backwards here.

John's = it belongs to John. it's != it belongs to "it".

Why that is, I don't know, but it's true. I assume it's to distinguish from "it is" and "belongs to it" because you don't have the same problem with "John is" being "John's".