By default, the Apt Maven Plugin executes apt within the current process. To execute apt as a separate process, use the fork configuration parameter as follows:
<project>
...
<build>
...
<plugins>
...
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>apt-maven-plugin</artifactId>
<version>1.0-alpha-4</version>
<configuration>
<fork>true</fork>
</configuration>
</plugin>
...
</plugins>
...
</build>
...
</project>