Ethics is also not as simple as "the author's wishes are always to be respected". For instance, free software was built on the ethical principle that restrictions on users' four fundamental freedoms (whether that be legal, technical, or in this case social), by IP holders, are unethical. This justifies piracy, and definitely justifies breaking this request.

I don't believe it is possible to reconcile these ethical views, as a ethical subjectivist.

I think there might be cases where the ethical thing to do would be to respect an author's non-binding request. However the request in this case seems directly contradictory to the principles of open source software and thus I can't bring myself to see it as legitimate.

Edit to add, an example of a non-contradictory request might be to contribute monetarily in proportion to the financial benefit you derive. It's an additional non-binding request to help sustain the community which seems reasonably consistent with the ethos of opensource to me.

The issue is that opensource is a movement that comes with a set of values attached. The licenses aren't impersonal the way the copyright system at large is.