the website and email links are made clickable only if the url and email hooks have been set before setting the 'website' and 'email' properties; if you set the hooks after that, the links won't be clickable.

the documentation should mention that the order is important, so a paragraph should be added, either in the main class description or in the hook setters function description:

'When setting the website and email hooks for the GtkAboutDialog widget, you should remember that the order is important: you should set the hook functions before setting the website and email URL properties, like this:

  gtk_about_dialog_set_url_hook (GTK_ABOUT_DIALOG (dialog), launch_url, NULL, NULL);
  gtk_about_dialog_set_website (GTK_ABOUT_DIALOG (dialog), app_url);

otherwise the GtkAboutDialog widget will not display the website and the email addresses as clickable.'