The project page is very unclear, so I ended up on Wikipedia instead. Wikipedia actually has a leaked memo that seems to do a really good job describing the purpose of the language.
Specifically, the language is meant for three environments: server-side, compiled to JavaScript client-side, and fast native client-side once there is browser support. (The main goal is better performance on the client-side, which is deemed to be very difficult with JavaScript.)
However, the language looks so Java-like, one wonders why they didn't just use Java and extend GWT with a native Java client in Chrome. Did it just not make sense to bet the farm on Java when Oracle controls it?
Also, what does the "structured" in "structured web programming" mean?