Better maven support has been frequently requested on the issue tracker and mailing list, and this is a first step in that direction. In the future, Google will publish GWT releases to maven central as part of the release process.
The GWT 2.0.4 jars currently in the repository include gwt-user, gwt-dev, and gwt-servlet. To publish these artifacts in the Maven Central repository, Google publishes artifacts to Nexus OSS, the Open Source oss.sonatype.org repository. You can see the Google-specific repository on this server here. Releases are staged to this Google repository on oss.sonatype.org and then subsequently released and synchronized to the Maven Central repository.