It's not currently possible in the OpenVDB API to do a shallow copy of a const grid while modifying the transform or metadata.

Discussed with kmuseth and pcucka shortly after ABI=5 was released and we talking about revisiting this for ABI=6 (but I think we all forgot).

This was pcucka's suggested work-around at the time:

I suppose it would be good to add optional Transform and MetaMap arguments to GridBase::copyGrid() and Grid::copy(). That would be an ABI-breaking change, though. For the time being, you could write your own copy function—maybe something like this:

template<typename GridType>
inline typename GridType::ConstPtr
copyGrid(
    const GridType& grid,
    const openvdb::math::Transform::ConstPtr& transform = openvdb::math::Transform::ConstPtr{},
    const openvdb::MetaMap& metadata = openvdb::MetaMap{})
{
    auto copyOfGrid = openvdb::StaticPtrCast<const GridType>(grid.copyGrid());

    openvdb::ConstPtrCast<GridType>(copyOfGrid)->insertMeta(metadata);

    if (transform) {
        openvdb::ConstPtrCast<GridType>(copyOfGrid)->setTransform(
            openvdb::ConstPtrCast<openvdb::math::Transform>(transform));
    }

    return copyOfGrid;
}

I'm tagging this ticket for ABI=7 so we can look at the changes to GridBase::copyGrid() and Grid::copy() sometime closer to the release of 7.0.0.