Yesterday, Jack Dorsey, Twitter’s original CEO, confirmed he was coming back to the company to head up product development, while maintaining his role as CEO at Square, the mobile payments company. Today, he’s talking about Twitter, as it refines its business model and manages its ecosystem. There are some good insights in this partial transcript. Dorsey maintains that Twitter has an effective business model and a revenue stream in place, but that it needs to communicate its future directions more clearly to third parties. It must inspire developers to combine technologies rather than create them: he calls out geolocation and mobile sensors. Twitter is aiming its own client apps at mainstream audiences – so TweetDeck is okay, I guess – and needs to work harder on improving the tweet-viewing experience, rather than the tweet-creating one. Dorsey says his mission is to help users extract relevance from Twitter.