Backgammon had a pretty large community at Yahoo! Games. With the demise of Yahoo! Games the only place to play online was FIBS, for which you had to download a Java client... Glad that finally someone scratched their own itch and built this, I will check it out and suggest it to my father.
Edit: Hey tslocum, rather than downvoting anyone who mentions other sites where people can play backgammon, I’d love for you to tell us more about why you believe your site is or will become superior to the existing options. There’s room for improvement in this space, but you’re definitely not there yet.
Check https://www.playok.com/ - it has backgammon as well as other games. The site is using html 5 and following "keep it simple" principle; it just works