It's developed by third party, not by developer, and not by the66, as he already told you.
Besides, there is no content with Alice.
Patreon didn't force FFCreations, this was stepsister story from the begining. Latter he added childhood friend option because of Patreon, they still consider stepcest to be incest. I think it's due to the fact some US states have legal prohibition of marriage between the step-siblings. Like somebody noted, developer and writer are active here, you can always check with them for more info.
That said, see the point above.
1) Story was not originally incest.
2) Incest mods are made 3rd party.
3) Ask for update at dedicated threads. Nobody is judging you for wanting it, but always try to ask at right place.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
4) You don't really need incest mod for this update, as it is ending about girl who is unrelated to MC either way.