Would be nice if you guys open source the detection code, similar to the way C2PA is open

That's like asking for Adobe to open source their C2PA signing keys.

AI watermarking is adversarial, and anyone who generates a watermarked output either doesn't care, or wants the watermarked removed.

C2PA is cooperative: publishers want the signatures intact, so that the audience has trust in the publisher.

By "adversarial" and "cooperative", I mean in relation to the primary content distributor. There's an adversarial aspect to C2PA, too: bad actors want leaked keys so they can produce fake video and images with metadata attesting that they're real.

A lot of people have a large incentive to disrupt the AI watermark. Leaked C2PA keys will be a problem, but probably a minor one. C2PA is merely an additional assurance, beyond the reputation and representation of the publishing entity, of the origin of a piece of media.