This is a good question. Lots of people, including me, have been in your shoes.
I don't have the answer you are looking for, really. Ultimately, my take on it is that if you will be consistently using someone's repeater/gateway for your D-Star operation, it is the right thing to do to support it, whether it's by joining the club, or making some sort of donation. Of course, you can usually do local operation in DV mode, just like you can FM, without contributing. But with gateway registration, the people who spend the good money to put up and maintain equipment finally have a nice way of prodding active consumers of THEIR resources into doing at least some minimal cost-sharing. 20 bucks per year or whatever it costs is not a lot to ask.
That said, I am sure that if you hunt around, you will find someplace to register that is not asking for this kind of nominal donation.
