It doesn't say anywhere that it's in "maintenance" mode.
But it's true that it could be more active: http://coffeescript.org/#changelog
https://github.com/ruby/ruby/graphs/contributors
https://github.com/golang/go/graphs/contributors
https://github.com/scala/scala/graphs/contributors
https://github.com/Microsoft/TypeScript/graphs/contributors
https://github.com/ruby/ruby/graphs/contributors
https://github.com/golang/go/graphs/contributors
https://github.com/scala/scala/graphs/contributors
https://github.com/Microsoft/TypeScript/graphs/contributors