I don't know any other way to do it, but I just purchased another full version (when I already have swf studio V3) to support this great application. Don't know any other way to donate, Tim please give us a way to get you paid so you can feel valued.
Others, if you feel so inspired, please do the same.
Adobe takes $1000 per year for creative suite, I am more than happy to pay $300 yearly for this software and the great personal support that comes with it. I have been able to do great things with it.
At least my 2 cents...