In UploadWizard, we use license tags as a last-ditch attempt to get the user to specify some sane license for the upload(s). It's the option for people who know what they're doing, but don't like any of the other options for some reason. Likely situations where it's necessary include many public domain tags that have to do with expiration of copyright, non-free licenses on third party sites, or obscure and currently-unsupported free licenses.
How to configure
License tags are configurable in UploadWizard! By default, the category for license tag templates is called "License tags", so simply creating templates that belong to that category and have the relevant license information should be enough to make it work. If you run a wiki that wants an internationalised form of the category, you can change the name of the category in the UW configuration by setting
$wgUploadWizardConfig[ 'licenseCategory' ] to whatever you want. For example,
$wgUploadWizardConfig[ 'licenseCategory' ] = 'Vignettes de permis';