Closure fell out of vogue because it's fairly heavy and seriously subsets javascript, which makes it convenient when you're compiling to javascript (from a very different language, not just augmenting/macroing it), but not when you're writing it by hand.

Something interesting is that I believe Google is working on a compiler that converts TypeScript to Closure, which would let you take advantage of the closure compiler while utilizing TS. That would be a very exciting development.

That's interesting. Are there any mailing list posts, issue links, etc. you're aware of that cover some details?

There's a JavaScript version available that has feature parity with the Java version.

https://github.com/google/closure-compiler-js

that's only a transpiled version of it:

    The Javascript version of the Closure-Compiler is
    transpiled by GWT from the Java source. For more details
    on the differences in behavior see the super sourced
    files in the main repo.

Is that an issue?

No.

(But it's slower ;))

Is that an issue? ;-)

Or because the only real build tool (Plovr) was maintained by a single guy and hasn't been updated in years.

I'm sure patches are welcome. Well volunteered!