Screenshot Captor is an excellent program - but the license key process is a bummer. Why? Not everyone is or was ever dedicated to using PayPal, not everyone wants to pay by credit card and not everyone wants to mail a check or money order and give out personal info. PayPal still owes me money that they wouldn't pay because I didn't draw every penny out of my account before I changed some personal details about my account. I can't even use that money to make a donation to anyone unless I send them some personal information they now require that has nothing to do with my identity. I was a long term PayPal user and did a lot of business with them before they became too picky and greedy.
A software developer who nags too much and makes it too difficult to use FREEWARE increases the chances of losing users that might have donated. Over the years, I've bought and donated for a lot of software that didn't nag. Software that gets too greedy will be dropped for another of the many freeware programs available. That's just the way it is.