Maciej, I'm sorry. Your interpretation of what I originally posted was not only reasonable, it was how most people read it. The fault was not yours, but mine. We changed the rules of a game you had won, to cover for my failure to anticipate an unwanted outcome, and you were right to be pissed.
We've offered Maciej the $20k, and he graciously accepted and asked us to donate it to the San Francisco Coalition on Homelessness (http://www.cohsf.org/). We'll take care of doing so. (Edit 2016-05-08: We now have.)
A note to HN users: The intention behind Apply HN was to do something new to excite and interest the community and engage it with YC in an interesting way. That did happen, but it pains me that it also partly turned into the opposite. If any of you have suggestions for how to do better, I'd like to hear them.