GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Website 2 APK Builder - Convert your HTML, CSS, JS and all other web content into an Android App within seconds.
PyQt - Riverbank | Software | PyQt | What is PyQt?
Median.co - Median.co (formerly GoNative.io) is the industry leading solution used to build iOS and Android webview apps. Get started for free and turn any website into a full-feature mobile app in seconds.
wxWidgets - wxWidgets: Cross-Platform GUI Library
WebViewGold - Convert your web apps and websites to iOS & Android apps in 60 seconds.