I redesigned the site a few months ago, and the donate scheme I had got left off. So I will fix that up. Thanks for reminding me.
But it became a bit problematic because Paypal donate buttons stopped working for Japanese Paypal accounts. I had to set it up an alternative way(using gumroad). And there are very few donations really.
Honestly teachers shouldn't feel any obligation to pay out of their own pocket. I would prefer that institutions bought support services as a way of contributing. They can be found here if anyone is interested. http://poodll.com/premium-support
Justin