They have clients in many languages. But the zig repo is still just a placeholder. They often have bare bones servers in the languages too, like rust has one, but I think they are mostly for testing.
I'll shamelessly plug this. I think this is the most complete NATS client for Zig, matching the official clients in API and features: https://github.com/lalinsky/nats.zig
In fact, working on this client prompted me to start working on another Zig project, asynchronous I/O framework, which I'll be integrating with the NATS client soon: https://github.com/lalinsky/zio