It is important not to automatically make assumption that all non-profits are impoverished and run by volunteers.
One of the most famous examples is Wikipedia.
Technically yes, they are a non-profit. Impoverished ? Certainly not !
Look at the financials, as others have already pointed out. Especially if you are in the habit of donating to non-profits, the financials can make for interesting reading.
If you look at lichess financials they currently have two full time employees - in this case it's not a bad assumption. Wikipedia has significantly more users and does fundraisers