I wonder how these kinda models work. I think that over time, while the userbase / costs increases, the donations won't increase as much / decrease. Is this true?
The website exists for more than 3 years, today we are the 7th of October and the donations are already at 100% for the whole month. It's arguably sustainable enough.
On a quick glance, I didn't even find a donation button. In fact, I found none, even after clicking through the menus (google sent me here: http://de.lichess.org/donate ).
I'm sure I'm not alone in donating just to ensure that development continues and it remains free for others to use. I don't get a chance to play many games a month but it's nice knowing that others will be able to get better at chess using their platform. Hope it continues to get more higher-ranked players playing there.