Finally! I’ve managed to write a Maven POM for Enterprise App. Just add this into your pom.xml file:
<dependency>
  <groupId>org.vaadin.addons</groupId>
  <artifactId>enterprise-app</artifactId>
  <version>0.4.0</version>
</dependency>
You might need to add the official Maven repository for Vaadin addons as well:
<repository>
  <id>vaadin-addons</id>
  <url>http://maven.vaadin.com/vaadin-addons</url>
</repository>
Better late than never ;)