I think you'd have to ask the Jamatto people to get a definitive answer, but just fiddling with an HTML page on my local disk I was able to get the donate butto

I think you'd have to ask the Jamatto people to get a definitive answer, but just fiddling with an HTML page on my local disk I was able to get the donate button to show a donation amount as low as 0.1¢, that is, $0.001.