100 USD a year (more in Switzerland because Apple doesn't even pay for the taxes) is not nothing. Why should I pay to place apps that I spend my free time to develop and offer for free? Apple should at least not charge a recurring fee if all apps posted are open source and free.
I'd also prefer if there was no $100 to pay. But it is a fair price, and I find the attitude of programmers that everything should be free quite damaging. If you want to donate your free time, that's really up to you. Don't construe constraints for other people or companies from that.
I don't recall the exact message, but I don't think they say it is damaged. They will probably say something like it may be damaged. Which is perfectly true, as they have no means of verifying its integrity.
At least over at Google it is a one time fee.