Hi DeltaJuliet,
" but what does it actually mean for RF?"
Here's an overview about RF's support for OpenVDB:
http://support.nextlimit.com/display/rf ... +-+OpenVBD
"and what does it mean for Cinema4d?"
Actually nothing, because currently C4D doesn't support OpenVDB ; - )
Well, that's more a joke and not 100% true. With some simple Graphs you can translate field data from OpenVDB files into Field3D files and load/render them with the RFRK which supports F3D. Another idea is to convert OpenVDB field data into meshes, save them as OBJ, for example, and import the meshes to C4D. The necessary Graphs can be downloaded from the link given above.
Cheers,
Thomas