The code is available on github - https://github.com/unterkoefler/xcuseme

I also wrote some notes on the development process (I rewrote the whole thing 3 times :)) and posted them on my blog here - https://www.unanswered.blog/xcuseme

The app was designed for mobile devices, so it will work, but look ugly, on desktop. The signup page asks for your email, but I'm using the free tier of IHP Cloud, which does not support sending emails, so I have no verification process in place. Also, like any IHP app, it uses nix for dependency management, so it should be straightforward to run locally if you want to try that instead.

Hope you enjoy!