What exactly is the Orange Catholic Bible?

In Dune what exactly was the OCB? Is it just a mix of all of Earth’s major religions?

From the glossary in the back of Dune :

Not having read Dune for years, I suddenly find that passage hilarious!

Laugh it up, Lobot … until Muad’Dib’s goon squad executes you for heresy!

Come on!

*“Mahayana Christianity?”

“Zensunni Catholicism and Buddislamic traditions?”*

That, my friend, is comedy gold!