Instead of rules, there is the code in the repository and a CI system that runs it on pull requests.

On each person's turn, they submit a pull request, which then gets discussed and voted on via reviews.

Files are marked either mutable or immutable: PRs touching only mutable files can go in with majority approval, ones touching any immutable files need unanimous approval.

There are tests, and the CI system ensures PRs can only be submitted over failing tests with unanimous approval.

The CI determines if someone has won and declares the winner.

You start with a file listing the usernames, and some simple code which will keep score and end up declaring a winner ~10 turns in the future if nothing changes.

This isn't quite as flexible as traditional Nomic because some things can't be changed (PRs, the infra the CI runs on) but is still very flexible. On the other hand, because it's all computerized, you don't need to have a system of judging anymore.

If you wanted to be really fancy you could implement this all in Etherium and have a monetary reward, but that's enough more annoying to program that I'm not interested.