From Zugg Software:
zApp is an programming environment for quickly developing user-customizeable and scriptable applications. Applications developed using zApp can be freely distributed without any royalty requirements. Any end user can run your binary application created by zApp. If a end user also had a developer's copy of zApp, they may customize your application to further suit their needs.
zApp programs can be written using any scripting language that is supported by Windows. Windows ships with built-in support for Visual Basic Script (VBScript) and Java Script (jscript). Support for scripting languages such as Perl, Python, ReXX, and many others can be downloaded from the Internet. Other zApp developers can also easily create plugins for your application using any of these scripting languages.