This POM is the common parent of all of the Maven components in the Apache Maven project. Most of its contents are pinning down version numbers of plugins; it does not provide any dependencyManagement.
This POM provides reporting profile for rendering documentation during site generation:
mvn -Preporting site mvn -Preporting site-deploy
See Plugins report for a list of configured report plugins.
As of version 21, this POM sets the Java source and target versions to 1.5. Thus, as any plugin (or other component) moved to version 21+ of this POM, it moves to requiring Java 1.5.