Though we don't have immediate plans for doing an alpha release of 2.6 or 3.0, I created an issue to knock over some of the items we'd need to do before such a release:
Daniel, you might want to check that the license/header changes I did match with what you expect.
P.S. I haven't merged those changes into GROOVY_2_6_X branch yet. There are some recent commits to master that need to be cherry-picked back onto that branch first.