I don’t think OpenVDB just works with Cycles out-of-the-box. There is a whole lot of work required to implement it in Blender, not something you just press compile and run.
I’ve been following his progress. He’s not quite ready yet. The issue seem to be that the OpenVDB SOC branch is a separate project from the SOC Dingto branch which contains the volumetric engine. So, he will have to wait for Dingto to commit his volumetric work to trunk before he can merge it into his own branch. At that point, you’ll be able to download the OpenVDB branch and play with it. I would estimate that’s at least a week to two week away.