After using the official release of DWR (3.0) we noticed it was better to use the release candidate RC2.
Here is the maven dependencies we used:
<dependency>
<groupId>org.directwebremoting</groupId>
<artifactId>dwr</artifactId>
<version>3.0.RC2</version>
</dependency>
Even we always tried to use only released final version of third-party software, we did not find any blocking issues in our project.