Livecode Builder is a new dialect of LiveCode in which you are able to write things called extensions. An extension will (in the first instance) either be a library or a widget - livecode.com 
Extensions come in two flavours:
The main aim of this clean up is to ensure we have a solid, predictable, reliable and completely defined base to work from without having to worry about any hangovers from the (very much organically evolved) past.
# See - LiveCodeish and LiveCodish - Emscripten