What's that on the top of every page on Wikipedia, Jimmy Wales's nonprofit encyclopedia? Why, it's an ad! Wales had long promised that Wikipedia would not carry advertising, but he makes an exception for the Wikimedia Foundation, Wikipedia's nonprofit parent. What Wales doesn't mention: Wikipedia will soon have many new ways of making money available to it, thanks to a revision in its open-source license. Wikipedia is switching from an obscure, restrictive agreement with its roots in software documentation to a much looser Creative Commons copyright license — which means the Wikimedia Foundation will be able to profit from its volunteers' editorial work. While they're at it, why don't Wales and company just run banner ads, too? The donation drive seems like an excellent opportunity to show potential advertisers how effective Wikipedia's ads can be.