Add a new dependency in your pom.xml and declare a new repository as Entropy is not uploaded into the central repository of maven:
<project>
...
<dependencies>
...
<dependency>
<groupId>entropy</groupId>
<artifactId>entropy</artifactId>
<version>1.0</version>
<scope>compile</scope>
</dependency>
...
</dependencies>
...
<repositories>
...
<repository>
<id>entropy.releases</id>
<name>Entropy releases</name>
<url>http://entropy.gforge.inria.fr/repos/releases</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
...
</repositories>
...
</project>
Download Entropy as a single JAR and add this jar to your classpath