This stupid law that is just the first step in further reaching surveillance, should be resisted. The first move should be to legally exclude downloading and use in California. I think it will even be necessary to remove all distribution methods (official mirrors) from California and have a contractual agreement on every download page.
I have read the actual law
https://legiscan.com/CA/text/AB1043/id/3269704 and my understanding is that it will require modifications to the package repo (and all mirrors) to prevent age restricted software from being downloaded or installed by a minor, and that to achieve that, EVERY package in the repo will have to be assessed and given an age rating. This means existing packages and every time a package is updated on the repo.
This is an enormous amount of work and could even include downloading from Git repos and other software source code repositories.
It is far simpler to change the licenses to have clauses that:
1. Prohibit the use of the software in California and other territories implementing the same or similar laws.
2. Prohibit the distribution of the software to anyone in California and other territories implementing the same or similar laws.
3. Prohibit the use of the software by all branches of the State of California Government.
4. Impose a contractual agreement for financial compensation paid to the software authors, publishers and distributors that is jointly and severally bound to all offenders that do not comply with the above clauses.
Yes, this is going to seriously affect the income of those doing business in California, but there is no other way.