If they just took a fundraising approach like how public radio and Wikipedia do, I would gladly contribute a few times per year when a big banner shows up asking for donations. That would be a nice direct value proposition -- "please contribute so we can keep this awesome resource free and high quality"
But paying for customizations? This seems like a distraction for all parties involved. It will take away product resources, it will make their code more complex and harder to work with, and worst of all I don't think anyone will really want it in the first place.
I truly hope I'm wrong, but so far this seems a questionable move.