Fan fiction and Mainstream Awards

The Tiptree Award is "an annual literary prize for science fiction or fantasy that expands or explores our understanding of gender." This year's longlist, which represents works that one or more of the awards panelists thought worthy of note, includes a work of fan fiction based on Harry Potter and CSI. Already, there's been much debate over whether an unauthorized derivative work should be considered for an award alongside professional/original works (you can take the scare quotes as read if you like). Naturally, whether the longlist is endorsing copyright infringement came up.

I'm not going to talk about the basic issue; I haven't changed my mind. But here's an interesting question: Assume that, rather than being on the longlist, the story won the award, and assume that the award carried a money prize. Would that convert the story from a noncommercial use to a commercial use? My instinct is no, but I'm not sure copyright law gives us much guidance. If I sell my fanzine at cost, or even below, or if I donate all proceeds to charity, those are all still commercial uses. But if someone walks up to me as I'm singing a satirical song to my child and says, "That's wonderful, here's ten dollars!" (in a non-hypothetical, the payment would certainly be to stop singing), I've made no effort to enter the stream of commerce. Precisely because so much counts as commercial use, it seems that one should have to take some volitional action to cross the line.