I'm not really sure what the purpose of the App.java and AppTest.java files are, but there seems to be a problem with them in this archtype. They have package declarations that match the project, but they are in $PROJECT_HOME/web/src/main/java rather than $PROJECT_HOME/web/src/main/java/**/ (replace "main" for "test" in the case of AppTest.java). I did see the following note in Core.java that I'm guessing is mentioning the same problem:

// There is no package since the Maven Archetype plugin doesn't support package expansion
// for multi-module archetypes: http://jira.codehaus.org/browse/ARCHETYPE-23.