When building a project with the archetype, one needs to either:

• use Maven 3 (which is probably fine, but we're still using m2 internally), or
• have magnolia-project:pom and magnolia-ui-project:pom in their local maven repository, or
• add

  <dependency>
    <groupId>info.magnolia</groupId>
    <artifactId>magnolia-project</artifactId>
    <version>${magnoliaVersion}</version>
    <type>pom</type>
    <scope>import</scope>
  </dependency>
  <dependency>
    <groupId>info.magnolia.ui</groupId>
    <artifactId>magnolia-ui-project</artifactId>
    <version>${magnoliaVersion}</version>
    <type>pom</type>
    <scope>import</scope>
  </dependency>