Earlier quoted context omitted.
Yes, of course it is fair. You can charge whatever you want for your program. But Ardour is free. Accepting donations is not the same as charging for something.
Technically speaking, ardour.org charges for a build service . You can get the source code for free from us (either as a tarball or via git). You can get the source code or the binary from somebody else. But if you want to get the binary from us, we ask you pay at least US$1.
I actually moved away from Apple/Swift development because of the limitations they place on you even if you pay (I cannot embed an interpreter in my iOS app, really?), and am now coding in TypeScript. So while the $100 are not a big deal, I think, it's a symptom of something that's wrong.