Well, it seems is a bit more complicated than that. It seem Patreon did not make it very clear, there are still today games where incest is inteqral part of the thing, and they have been for years happily on Patreon.
Honestly, one thing is incest being legal or not (first reaction, no, but it turns out, there is some USA state where brother and sister cannot marry, but can have sex without problems), another is whether its depiction in a work of fantasy, which is not made or distributed from Califormia is (Zorlun is not from USA), can bring legal chargest against Patreon.
Effectively, Patreon told Zorlun he could not distribute, or be involved with, any incest patch, even if it was distributed on another platform anywhere on the Internet, and never mentioned or distributed through Patreon.
It was already pointed out it is more a matter of internal rules and moral control, even by credit card issuers (although credit cards are widely used by people for porn, which has real people), than a real legal danger for Patreon from the State.
We had an exchange about UK law with someone.
It seemed the law (found the specific law about incest I think from '58, apparently the last), linked it to blood, so "step" or adopted would not apply for "incest", however it was already indicated that they anyway prosecute using formally different possibilities, though then people understand (or they say explicitly) that is due to the "step"/adoption.
The mention was that in case of "step", they will not prosecute if the stepson or daughterr has not lived with the stepmother/stepfather in the period of time before becoming 21 years of age (that also suggests that formally, they may be charging saying something like exploitation of the minor by taking advantage of the authority, or something similar, which woudl be usable in many countries).
I would not bet California and UK really have the same identical law about this, but if you say so, I guess I will just have to trust your word.
About the incest patch, there is alredy an incest patch, I make it
, though unfortunately it does require manually checking and editing the code.
Zorlun cannot participate (for Patreon, and due to time) in its creation or distribution, he cannot even tell people they should install it (aside the fact not everybody wants the incest possibility), but that does not mean we cannot have exchanges, on this forum, about it, with him, including on the impact/usefulness of the "legal guardian" to help continuing that line.