I made two small patches.
Incest Patch: Just copy "ipatch.rpy" into the "game" directory. If the developer doesn't change anything in the current naming convention, the patch should work for future updates as well.
Gallery unlock: Just copy "gallery_unlock.rpy" into the "game" directory. Again, the patch should be functional on future updates.
Only with the Achievement Scenes the developer breaks the workflow a little. Here he uses other variable names and statement types. On one hand, this means that they will have to be added manually in future updates (in the patch, see the "names" dictionary). On the other hand, these are variables that are stored in the savegame and I have no idea if this destroys anything in any scenes.
TLDR: There are some variables that are stored in the savegame and may affect the scenes. If you don't care about that, you can set the variable "full_unlock" in the file "unlock_gallery.rpy" to True.