There was a bug in Velocity 1.4 that was causing a spurious error message to be printed:
[ERROR] ResourceManager : unable to find resource 'VM_global_library.vm' in any resource loader.
[INFO] Velocimacro : error using VM library template VM_global_library.vm : org.apache.velocity.exception.ResourceNotFoundException: Unable to find resource 'VM_global_library.vm'
This affects many Maven users who include JXR reports with their site generation. That is because JXR uses Velocity, and thus the innocuous error would be displayed on every "mvn site".
With the release of Velocity 1.5 in 2007, the bug was fixed:
But even when using the latest versions of JXR (2.2) and the Site plugin (2.1.1), the error message still appears. This is because in the dependency tree, the old Velocity 1.4 release is being pulled in (see attached build log).
The component with a direct dependency on Velocity 1.4 is maven-jxr (not the plugin but the library). Updating it to use Velocity 1.5 would presumably cause the error message to go away.