Grails - An Open Source, full stack, web application framework for the JVM
Siberian CMS - Siberian is an Open-Source and Free App Maker. Unlimited Push Notifications. Unlimited features. Fully Customizable. Download it and build your own app now!
Vaadin Framework - Vaadin is a web application framework for Rich Internet Applications (RIA).
GoodBarber - GoodBarber is a mobile app creation platform.
Spring Framework - The Spring Framework provides a comprehensive programming and configuration model for modern Java-based enterprise applications - on any kind of deployment platform.
Bizness Apps - Create your own app or become a reseller and build apps for others