Again, the licence fee is effectively a tax on every U.K. household that uses a television. That is imposed by legislation and collected by the BBC on behalf of the government. A commercial revenue is dealt with separately by BBC Worldwide, and yes, indeed, they do all the things you might expect. They run commercial channels, which are not BBC-branded in the U.K., but they also publish books, sell programs to other broadcasters, and publish DVDs and other merchandise, as you say.
On January 29th, 2008. See this statement in context.