I've found documentation that explains how to render ES2 forms using a Java servlet, however I'd ideally prefer to integrate forms into a JRuby on Rails or Grails application. Would anyone happen to know if this is achievable?
LiveCycle has a Java API and an ActionScript API. LiveCycle services and applications can be called from .Net clients via SOAP, also. ES introduced REST endpoints on most services and all applications. You could call the LiveCycle Forms service from JRuby using NET::HTTP.