Hi, I like the idea of off setting purchases in this way. What I am wondering is how does the App developer make money? Apps need to be maintained and continuously improved. Normally apps will take a %ge of the donation or charge a SaaS fee if its a b2b product. 

You might be able to build something like this for 30-40k....but there will always be maintenance costs. 

Realise this is an old post =) was searching the www for something completely different and houd this