Hi John,
As you stated correctly, you should indeed seek help from the maintainers of that library, if there still are any – the last commit was made over three years ago. Even if you can make it work, that code implements the legacy version of the protocol that is not recommended for new designs, as I wrote at Yakut monitor with a Babel - #7 by pavel.kirienko
I would rather suggest considering this modern replacement for Arduino (not sure whether it suits your needs well but it’s modern and well-maintained): https://github.com/107-systems/107-Arduino-UAVCAN. Alternatively, consider going bare bones and integrating raw libcanard directly (this might be a bit more involved though). If you chose the latter, you may benefit from these demo applications we posted here: https://github.com/UAVCAN/demos