One thing that always hurts OpenSource project is the fact they have not ability for me to "Buy" it, with an actual invoice or receipt that I can give to my accounting people for the sale...

It is "donation" of a undetermined amount which is a much harder thing for me to clear the bean counters.

So by being able to go to a site, it buy now with a fixed price, and (I presume getting a receipt) you likey having gotten much more income than if you where to have a "donate to me" link with a open ended amount...