uavcan-v0.5 is an experimental port of libuavcan v0 to run on CAN-FD. while functional it is a dead-end as all available development efforts are going into libuavcan v1 “bluesky”. This new v1 branch will support both CAN 2.0 and CAN-FD and may support other real-time networks in the future. It will be based on the new UAVCAN v1.0 specification, will be header-only, and will require C++11 at minimum to compile. You can read more in the bluesky README.md (link omitted because the README.md will move when the branch renaming occurs).
The uavcan-v0.5 branch will be maintained until the end of 2020 (Jan 1, 2021) at which time this branch will be deleted.