More than simply reporting, “Package X uses license Y,” the FOSSology tool attempts to analyze every file within the package to determine its license. The license report is thus an aggregate of all of the different licenses found to be in use by a package. A single package may be labeled as “GPL” but contain files that use other licenses (BSD, OSL, or any of the hundreds of other licenses). Even if an exact license is unknown, the license may be identifiable by common license phrases.
This may be a service we want to run on cvs.drupal.org to ensure license integrity.