I worked for about three months on coding and two weeks on the concept. Yes, even though it's strongly inspired by Stackoverflow, it still requires some thinking about the implementation (especially the i18n stuff).

It was developed by @mitsuhiko and it has taken some work (you can check out the source code on http://bitbucket.org/plurk/solace/src/tip/solace/ - it's not a simple project). That said, it has not taken a lot of time, because mitsuhiko is a ninja ;)