For some weird reason, the SmartGWT dependency used by the web-explorer application uses the smartgwt groupId:

<dependency>
  <groupId>smartgwt</groupId>
  <artifactId>smartgwt</artifactId>
  <version>${smartgwt.version}</version>
   <type>jar</type>
</dependency>

This is only available in the public JBoss Nexus via the Third-party uploads repository, but it's not the official/correct dependency (based on Maven Central). The correct version should use the com.smartgwt groupId.