Curious: what class is it that you're using this API in?
Mental model shift: you don't add the Common Map Widget API to your OWF installation. You reference it as part of your widget itself. (Caveat: you could bundle it as a WAR and add it to the web server that OWF depends upon. That's not adding it to OWF itself: it's serving it up from the same web server. But then rather than referencing the Javascript, etc, locally from within the widget, you could reference it from a URL on your web server.)
I'd try communicating with the editors of the Common Map Widget API, listed on
http://cmapi.org/community.html, and see if they can point you to some specific example widgets that you can model from.