CBOR is MessagePack. At least cbor-ruby started with the MessagePack sources. There's nothing at all complicated about MessagePack, there are a few types, they all have small prefixes, end of format. The story is that Carsten took MessagePack, wrote a standard and added some things he wanted, and called it something else. I personally think this is pretty bad faith, but I admit I haven't been involved in the community or discussions, so it's possible there are some things I don't know.

Disclaimer: I wrote and maintain a MessagePack library.