The stated goal of the GeoScript project is to provide a geoprocessing library that is easy to use and available in a variety of scripting environments. It uses the same GeoTools library that GeoServer is built on, which means there is a wide range of things that can be accomplished with GeoScript:
Support for a range of spatial formats
The ability to render spatial data, including control over styling
Support for different projections and coordinate systems and the ability to reproject data
A wide range of geometry manipulation functions
GeoScript itself is a wrapper over the core GeoTools API, providing a layer of abstraction and making the power of the GeoTools library accessible to non-Java developers. GeoScript has its own API to access the core set of functionality from GeoTools; however, due to the way that it is built, it is possible to call any method from the GeoTools API directly. So, if you are a GeoTools developer or can work your way around the documentation...