Why isn't the 'single maintainer problem' a concern with other programming languages? What language DOESN'T have a single organization leading its development? Even worse, some projects (incl. coffeescript) seem to be controlled by just a handful of individuals who can easily be hit by a bus, hired away to do something else, lose interest, etc.

I think the only way to defend against that is to have an open source project, and to have a sufficiently large user base such that someone is sure to take over if the owners drop the project.

I think the strength of GWT is that for some languages/teams, a statically typed language is more appropriate than a dynamic language. And isn't more choice a good thing? Avoid the whole 'this is a hammer, everything else is a nail' approach?

I do agree that some teams choose GWT for inappropriate reasons though.