The #GtkAboutDialog will automatically fill out a standard disclaimer and link the user to the appropriate online resource for the license text.
If [gtk.types.License.Unknown] is used, the link used will be the same specified in the #GtkAboutDialog:website property.
If [gtk.types.License.Custom] is used, the current contents of the #GtkAboutDialog:license property are used.
For any other #GtkLicense value, the contents of the #GtkAboutDialog:license property are also set by this property as a side effect.