The license of the program, as free-form text.
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
GTK_LICENSE_CUSTOM as a side effect.
The text may contain links in this format
and email references in the form
<email@example.com>, and these will
be converted into clickable links.