In short - GPars is now using the Java 7 concurrency artifacts. Russel Winder has taken initiative and with an official blessing from the jsr-166 team he mirrored the most recent jsr-166 artifacts into the maven repository. This allowed us to remove the dependency on the ancient coconut clone of the fork/join framework and use the "real" live matter. With all the improvements and fixes that jsr-166y has gone through during the last couple of years this has immediate effect on GPars plus once Java 7 ships with jsr-166y bundled, we will be ready.
Nothing changes on the user side of things, provided you're using an automated dependency management tool such as Gradle or Maven. The recent 0.12-beta-1 snapshot correctly declares the new dependencies. You may check out more details in the snapshot user guide.
Enjoy concurrency in Groovy!
Yours GPars Team