It used to stand for Black Reparations Fund, but it turns out we can't legally do that, so now it means, "Bike Riding's Fun!" or "Bikes-R-Fantastic." In either case, we donate all BRF funds collected from the sale of these buttons to charity. (That's about $4.50 per button, in case you're wondering.)
We put these funds into a separate bank account, not connected to the general Rivendell one. We hope you'll toss one into your basket.