Still, there are lots of places you can’t put such a statement in. It’s polite to talk about those whose work you benefited from. An about page on your blog/forum with a link would be enough. Or maybe somewhere near where you put your advertising, a link with the logo of bbpress. Unitrusive and can even be pretty if you make a nice banner.
Feel free to use it as reference, but it’s like nothing I’ve ever seen done in bbPress. Like, at all. And not only the looks, functions too. I’m especially proud of the support of bbcode, including nested