It would help to know what your widget actually did, but here's a freemium pitch: make your widget free for the first X views / mo., and then show ads, unless y

It would help to know what your widget actually did, but here's a freemium pitch: make your widget free for the first X views / mo., and then show ads, unless your user subscribes for $Y / mo. By show ads, I mean, after some domain has gotten X views, break the widget and show the biggest ad you can.