License
I noticed the only reference of a license in this repo is the "license" field in the package.json file suggesting it is MIT. I'm not sure how intentional this was, since it appears to be left at the default value.
I would personally be happy with (A)GPLv3, however I believe that would be incompatible with the Apple App Store, because they block users from making and applying modifications to the app. iOS users would be unable to use the native app, but they could use the PWA, and even take advantage of the (A)GPL by making modifications to the PWA and redeploying it.
Either way I think a license file should be added to avoid confusion.