I had always assumed this just meant that you couldn't inject paid ads into the actual Twitter feed, but reading this in detail you are right, you can't simply mix paid and Twitter content within the display of your app.

Moreover the Twitter API TOS seem to forbid the notion of other sponsorship and advertising for this widget unless Twitter also gets a cut:

> "In cases where Twitter content is the primary basis of the advertising sale, we require you to compensate us [...]"

It sure sounds like this widget is all about Twitter content.