I started a fork of this project on Github at https://github.com/nickman/javax-scripting.
Initially I am moving over just the ones I really need, and I will follow with ones that do not have JSR-233 implementations out there already.
The project is mavenized and I am packaging all the implementations into one artifact.
Bear with me, I should complete it shortly. Please post an issue if you have any questions.
As far as the fork goes, I would categorize the changes into 2 groups:
The fork is in maven format which makes the project more "consumable". The original project only exists in source code, and there are no downloads, artifacts or javadoc available. This maven fork will provide ready to use jar artifacts, as well as javadoc and source attachments. In addition, rather than producing one jar per engine, I am packaging all the implementations into one artifact. In general, I am not modifying or adding to the source code, except that I am attempting to provide javadoc for all public and protected methods. I am adding the required maven poms, and as best as I can, I am defining the dependencies against published artifacts in the Sonatype public repositories.
In a separate sub-project, I am extending some of the current engines to use Java 7 Invoke Dynamic instead of reflection for runtime invocation. I don't have any hard numbers, but by all accounts, this should significantly improve the performance of some of the engines. I have some ideas for some other enhancements, but they're more experimental.