Earlier quoted context omitted.
> Now, if you saw a banner ad for that on lichess, would you really feel awful about it? Frankly, yes. Lichess is such a relief because I know it's a place I can go without someone trying to sell me something.
Did you donated to it ? Because this is possible only with donations. I did, but if at some point they will have to add some ad, I won't consider that awful if done in the right way.
Why? Plenty of sites are able to survive solely on a donation model, even large ones. Look at Wikipedia.