Alternatives:
1. Webview: https://github.com/zserge/webview
2. Lorca (Chrome): https://github.com/zserge/lorca
3. Carlo (js/Chrome): https://github.com/GoogleChromeLabs/carlo
zserge’s webview has been adopted by a bunch of maintainers who made Rust bindings for it. They have forked webview to continue maintaining it, and are now gradually rewriting it in Rust.
https://github.com/Boscop/web-view
Made on top of that is Tauri, a cross-platform webview-based app just like WebWindow. The key differentiator being that they are actually committed to continuous development as they’re trying to get established as an open source company.