It's much more meta, for one thing. SO had a topic: programming. Here we don't have any particular topic, our goal is to make your topic successful, whatever it

It's much more meta, for one thing. SO had a topic: programming. Here we don't have any particular topic, our goal is to make your topic successful, whatever it is, through open source software and community. In other words Discourse is only successful in the sense that it lets you be successful.