Seeing the downvote, let me add relevant context - VLC is one of the most awesome products I have ever seen that is open.

My feeling is that an equally great “open App Store” that is popular enough does not exist (and if it did, I suspect Apple for example would actively have prevented it from being an option on iOS). Probable Google too for Android? I am not as sure in the second one.. is there an open Android App Store/marketplace/catalog?