There's a ticket on our backlog regarding the "signatures for FREE users workflow". We will review and make this as easy as possible.
The problem with donations is that it doesn't work very well with companies, for legal reasons. That's why we prefer people purchasing a license (the price is very reasonable) even if they don't really use it. It's just a way to get something in return, but I know what you mean. It's always a matter of balance...
