It uses the postgresql interface so any Postgres compatible client should work. The status just refers to esoteric features that may not be supported.

We marked these drivers as beta support to indicate that we haven't tested them to the same rigor as our internally developed features. Basic querying and transactions should work with any of these drivers, but features like introspection and less commonly-used data types haven't been extensively tested across all drivers. Many people report using these drivers in production, however, we've prioritized new feature development for CockroachDB over extensive driver testing. We encourage you to give these drivers a try and let us know if you encounter any issues--we'll be happy to fix any bugs brought to our attention.

They haven't any custom driver, CRDB is binary compatible with postgresql drivers, are marked as beta because "maybe" there is feature they haven't implemented. So far using pqxx (C++ driver) I haven't seen any issue.

it uses standard, off the self postgresql libraries. but their server-side implementation of postgresql isn't 100%. or even 98%, so you can't count on every feature of every client library working.

Most seem to just be postgres drivers.