Weird right? But true according to GigaOm today, who go on to explain that nearly a third of the top-grossing iPhone apps today are free. Confused? Don’t be – it’s about in-app purchasing. Since Apple opened the floodgates with the in-app idea, freemium apps have flourished.   Free apps have the advantage of encouraging downloads, obviously because they’re free, and then once you’re hooked on the app they tempt you with in-app goodies. And it’s not just gaming apps that pay the bills for free, social media, and of course notably Facebook with Farmville, is a classic example. The iPad is not as lucrative in this market, as yet and…