This is what professional support contracts are for. If someone really wants something implemented that is of no use to anyone else, then they should pay for it.
Not everybody wants to make a career out of their side project. Just because you offer me money, doesn't mean I should be obligated to take it. (By all means, offer the money to somebody else, just leave me out of it.)
I'm ok with that. What I'm not ok with is when people use open source as an excuse for mediocrity. Many times you do hear "It's open source, I'm doing this for free, just fork it!" when it probably should be "It's a hobby project, it probably won't go anywhere and the code wasn't really made to be used by someone else, but if you can find something useful you're free to use it". There are a lot of active open source projects out there that spend a lot of time maintaining their project and I think it's kind of "meh" to undermine the positive things they've been working for.
I have absolutely 0 problem with this, as long as a disclaimer is listed like the OP did. I honestly think this is the right way to do it. Imagine though if apache had some major security flaw uncovered tomorrow and the maintainers said, "This is just an open source project. You are free to look into the issue and fix it yourself if you want. We will merge the pull request when we get around to it.". Managing expectations is-- as usual-- everything.