He basically had this option, and it's the way that Rich Harris and the Svelte team went a few months back by adopting JSDoc, and honestly his reasoning for dropping typescript in favor of another typing system is pretty sound and did result in clear benefits for both users and maintainers.

DHH has something specific against types in general which I really don't understand. And that's fine, I'm happy to let him and 37 signals do whatever they want. I probably won't be super duper interested in applying to work on basecamp/hey, but that's his choice and I'm sure there are devs there who do prefer it. It sounds like they've been doing it for a while.

But this is an open source project with users and contributors outside the company. It absolutely can and will impact those people. Types supercharge your IDE with better linking, docs, and error detection. It will be harder to work on and around this project, and many current open PRs now will need to be refactored, and the way people build things will need to change.

And that wouldn't even be so bad if the proposal had come out more than a few hours before the merge. It's clear that no community engagement was even considered.