The following is the latest information on VDB Volumes, which has not yet been added to the on-line manual.
Loading an image sequence using the VDBVoxel Source Filename property
Modo does not provide any way to determine if a Source Filename is an image sequence or just a single VDB file (as it is not a normal Image Sequence that you would find in the Shader Tree). Therefore the plugin tries to load the actual VDB file in the Source Filename (which is for frame 0), regardless of which frame is being rendered.
The current workaround for this situation is to load the VDB sequence in Octane Standalone (as an image sequence). To do this, start with a blank nodegraph in Octane Standalone, rightclick the nodegraph and add a Geometry->Volume (assign any .VBD to the volume). Then select the Volume node and click the "Assign new volume animation" button and load the entire sequence.
You will also need to setup the Volume Material in Octane Standalone (by right-clicking the nodegraph canvas->"Medium"->"Volume medium" and attaching the new Volume medium node to the Volume node's "Volume medium" pin). Then attach the Volume node to a Geometry Out node and then save it to an ORBX file (using the File->Save as package menu option).
In Modo, set the file saved above to a blank Modo Mesh->Octane->Proxy Filename property. The VDB sequence should now render correctly in OctaneRender for Modo. You can edit the ORBX proxy by selecting the blank Modo Mesh item, and clicking the "Edit Proxy File" button. To save your changes to the ORBX file, click the "Save Proxy File" button.
Make sure you turn Kernel->Animation->Camera Motion Blur ON if using this apprach.