There are a few valid arguments that I see to support the pessimism:

1. When people use LLMs to code, they never read the docs (why would they), so they miss the fact that the open source library may have a paid version or extension. This means that open source maintainers will receive less revenue and may not be able to sustain their open source libraries as a result. This is essentially what the Tailwind devs mentioned.

2. Bug bounties have encouraged people to submit crap, which wastes maintainers time and may lead them to close pull requests. If they do the latter, then they won't get any outside help (or at least, they will get less). Even if they don't do that, they now have a higher burden than previously.

Bug bounties had this risk from day one. Any time you create a reward for something there will be people looking to game it for maximal personal benefit. LLMs and coding agents have just made it that much easier to churn out "vulnerability" reports and amplified it.