There is no script at present. As I understand it, Texstar's getvirtualbox is a script which downloads the application plus the additions ISO and the USB extension pack. Because the last two are PUEL they can't be packaged (or so I believe), so they either have to be added manually or using a script similar to getVB.
However, the base application, which is all some people will need, is open source and can therefore be packaged, and as that makes it easier for users to upgrade (no need to run a script, easy to transfer downloaded package to second machine etc.) I would think it the more elegant solution.
GetVB arose because Oracle stopped packaging the PUEL version for pclos, but now there is no PUEL version, just the OSE plus an optional PUEL extension pack.