Lichess is a free/libre, open-source chess server powered by volunteers and donations.
In 2010, Thibault Duplessis began work on Lichess as a hobby project. The site was simple at the beginning, not even checking to see if moves were legal. He made the site open source, which means anyone is free to read the source code and make contributions. Gradually, the site improved and collected users as an enthusiastic volunteer staff assembled to help Thibault build and maintain the site.