This is not the actual RC4 released zipball, it's just the automatically exported zipball of the play sources tagged with 2.0-RC4.
The difference is that the released tar|zipballs contain also a prefetched sbt cache repository.
Furthermore the zipball has the play version as "2.0-SNAPSHOT", so you have to change that in framework/build if you want to fetch the released 2.0-RC2 binaries