it uses Android's webview, which is a chromium browser that comes with Android by default to be used inside apps. This means that it does not need to be updated frequently, since it is just a wrapper for Android's webview. And bookwyrm itself is updated on the server side and sent to your browser, so no need to update that locally either.

From reading their github's repo, the only thing the developer adding is a barcode scanning for books to be used within webview. Not sure how many updates that thing needs, probably not many.

In conclusion, as long as webview is updated (important, browsers are a security nightmare) and your Bookwyrn instance is updated too, there should be nothing to worry about even if the app itself isn't updated in a year or more.