Can't Tell the Forest for the Trees
One big reason Jackpot hasn't released yet is because it is tightly bound to javac's private modeling API for abstract syntax trees (parse trees), types and symbols. The two teams have been working together on how such an API can be exposed without locking down javac and preventing future innovation.
The solution the javac team designed is an interface-based AST abstraction, which javac will implement while still keeping its internal implementation private. This, along with the proposed enhanced Mirror API that is part of JSR-269: Pluggable Annotation Processing API as well as JSR-199: Java Compiler API, will be the only javac API that Jackpot developers will use.
Interested? Peter von der AhÃ© has a blog entry describing how to join
Tree API project. See you there!