When an independent, Democratic fund-raising group was launched last week by former White House aides Bill Burton and Sean Sweeney, one of the reasons for going outside the traditional finance system was to counter the flow of funds flowing to like conservative orgs — including money coming from the Koch Brothers.

The billionaires are now the subject of a series of videos coming from another independent org, Robert Greenwald’s Brave New Films, with the focus of the first on the multiple homes they own. Greenwald has disclosed a list of Brave New Films’ donors to the New York Times, and notes the bulk of their donors are not only low dollar, but already posted on their website.

There’s a reason behind it: Brave New Films is set up as a 501(c) organization in the tax code, meaning it doesn’t have to disclose its donors. Last year, President Obama criticized the rise of conservative groups set up in a similar way, and Democrats have long suspected that the Koch Brothers are big bankrollers of such election spending.

More than likely, such outside fund-raising groups are only going to grow. Burton and Sweeney’s org, Priorities USA, includes a 501(c) arm in addition to a political action committee. Jeffrey Katzenberg, who provided initial funds, and his political consultant Andy Spahn will be among those tapping very high dollar donors from entertainment and other major cities to contribute.