I don't understand what problem this project solves and whom it solves it for. We can already manage multi-site WordPress installations and usually that's done by site admins, not the average content Joe, so does it really need a super fancy new UI?
And what exactly does it mean when you say "WordPress.com is open source"? Maybe I'm out of the loop but the way I understand it is that wordpress.com is a hosted (commercial) service of wordpress.org.
My experience with WordPress is not that the UI is a problem at all, neither multi site management, which I think is in the scheme of things quite niche. The problem with WordPress I hear other developers complain about is the out dated PHP system architecture.