The license of the program. This string is displayed in a
text view in a secondary dialog, therefore it is fine to use
a long multi-paragraph text. Note that the text is only wrapped
in the text view if the “wrap-license” property is set to
otherwise the text itself must contain the intended linebreaks.
When setting this property to a non-
NULL value, the
GtkAboutDialog:license-type property is set to
as a side effect.