crabflip is free, has no ads, and doesn't sell your data. If it's been useful and you want to throw a few dollars at keeping it running, it's genuinely appreciated -- but never expected.
This isn't going to become a paid product asking for your bankroll on top of your bankroll; the honest scoring, the killed hypotheses, the whole point of this thing is staying straight with you. A donation just helps cover hosting and the time that goes into keeping the backtests honest.
(Placeholder -- no donation account set up yet. This link isn't live.)