No, it's very forward compatible, but the amount of facility now available at the current release includes all of the advanced ""event scripting"" (triggering off of events in the life of a data element) as well as recent UI event support. I believe much of what was presented in the 4.3 was BOI (Business Object Interface) or ""outside the box"" scripting aside from button scripts that had no access to the business object model that was introduced with 4.X.