Closure Stylesheets is now available on maven central as a third-party upload.

<dependency>
      <groupId>com.google.closure-stylesheets</groupId>
      <artifactId>closure-stylesheets</artifactId>
      <version>20140426</version>
  </dependency>

The project has been cloned to github.com/StefanLiebenberg/closure-stylesheets and adapted to build with maven.