Need some info... – Darkr - Black And White Filter Review

So this developer has another app that looks exactly the same that goes by the name Darkr. I am certain this has been asked plenty of times, but can someone please, in simple language, explain the differences between the two if there is any? And if they are the same why not simply remove one of them from the App Store?
Review by John Katz on Darkr - Black And White Filter.