This is a preparation exercise for the task "Make the scale bar configurable by adding a settings page":

The scale bar plugin should receive an about dialog which displays the copyright notice, the license and all the other data that is usually displayed in the other plugins in this place.

Have a look at

http://techbase.kde.org/Projects/Marble/OnlineServices

and at the existing Online Plugins. The Wikipedia plugin has got an about dialog  that you can use as a "template".