JSR223 allows you to write scripts that create rules, or it can be used inside rules, but it can do MUCH more. In the new rule engine, there are Modules (Triggers, Conditions and Actions), which are further broken down into ModuleTypes. I am wrapping up ModuleTypes that will allow a script made with any JSR223 language to be used in a Condition or Action. I am also working on bundles to ease the installation of Jython, Groovy, and the helper libraries. After those, I plan to address the scripting API and creating more ModuleTypes (aka, more options in the dropdowns when building a rule in Paper UI).
Layers of abstraction… these are being built so that you can drag/drop, point/click, etc. your rules in a graphical interface, or so that you can do complex things in a script with simple commands. The rules DSL provided abstraction for the old rule engine. For the new rule engine, there are ModuleTypes (mostly for use in the graphical interface), a scripting API, ScriptExtensions, and language specific helper libraries for areas where the API has not yet been built out.