Donations and other giveaways are tax deductible. What if you offer a freemium software model? Could you find the fair market value of the free product and deduct the cost of the non-converted (still free) users? That is FMV x NUM_FREE_USERS = DEDUCTION ? We all know that there's work to keeping those free users using -- sometimes more than paid users. There has to be a model for addressing the resources put into supporting them.