Looks mostly like an iSCSI target for Ceph. Based on their website running at least one LTS release of Ceph behind current (still on Hammer).
I had always wondered why the Ceph team didn't deliver this capability natively. Doesn't seem like much of a stretch to go from the Linux RBD to iSCSI. Probably just a matter of priorities and some degree of 'Linux bigot' attitude amongst the developers. It certainly opens the market much wider than just RBD/kRBD.
Frankly I've also always wondered why they don't do a windows driver for CephFS rather than forcing people to use a Samba/SMB server to intermediate. You lose the scale-out properties of the system when you force it through a single host bottleneck.