I really liked the book “Implementing SSL / TLS Using Cryptography and PKI”. When trying to understand certificates and TLS, there always seemed to be some tricky bits that most explanations glossed over. In this book, the author builds a working TLS implementation in C, which means they have to cover all the details.
In the US at least, it would be the patent holder’s choice if they want to license their patent (in most situations, if I understand correctly). When I patent advertising on vegetables, I won’t let anyone license it.