I allow them to train on my work as described here (for example) https://code.claude.com/docs/en/data-usage

And I do paste code into CC. I’m not super concerned that they’ll see it.

That’s fine by me. It doesn’t require putting code in the public domain which is something else entirely.

I make money off hosted software so in some sense there is writing involved at one end. But I’m not paid by output tokens.

If your code isn't in the public domain, then anything you haven't explicitly allowed them to train on is restricted for them. They've been ignoring that for anything they can actually get their hands on, but it's there.