This site is one of the best things I've seen on the internet. It inspired me to make a similar site for crossword board games (think Scrabble, Words With Friends, etc). See https://woogles.io - also AGPL. The backend is Go-based, and the site has around 6500 MAU (we're about to hit 2M total games). We just released a puzzle mode that is pretty popular and is already making people improve - some of us anecdotally report better word-finding in live tournaments :)
It wasn't obvious to me (though I may have blundered to see/search) from the site where the code is, so to save others the search it seems to be at https://github.com/domino14/liwords ... the repo name underlines the source of inspiration I guess!
