Custombuild 2.0 is still beta, if you want to gather more information about the project you should contact smtalk on the forums.
I think Custombuild 2.0 is not in beta anymore since DA 1.42.x....
and of course RC1 means Release Candidate 1, which of course means that while it's almost ready for release, technically it's still beta.BUILDSCRIPT_VER=2.0.0-RC1