Wikipedia
OpenLaszlo is a discontinued open source platform for the development and delivery of rich Internet applications. It is released under the Open Source Initiative certified Common Public License (CPL).
The OpenLaszlo platform consists of the LZX programming language and the OpenLaszlo Server.
LZX is an Extensible Markup Language (XML) and JavaScript description language similar in spirit to XUL, MXML, and Extensible Application Markup Language (XAML). LZX enables a declarative, text-based development process that supports rapid prototyping and software development best practices. It is designed to be familiar to traditional web application developers who are familiar with HTML and JavaScript.
OpenLaszlo Server is a Java servlet that compiles LZX applications into executable binaries for targeted run-time environments.