Nobody forces you to pay and because gpsp is gpl licensed Zodttd will have to release the source of his work.
Nothing to get nervous about.. only excited.
I also think it's not helping the development of any new piece of software that a dev is putting
lots of hours into. I'm sure he would make lots more money working all those hours for a company than the couple of donations we throw at him.
It's always a treat to read the threads of Zodttd, he's a very enthusiastic developer and I hope he stays that way.
I'm sure that after some tiring hours of programming a dev will not be glad if his motives are being questioned, even if it's by a very small minority.
Don't bite the hand that's feeding you.. just be patient