Leave it to California to be the “Lewis & Clarke” of taxes! Always finding new ways, new items, new horizons to tax it’s people on. If you live in California, you’re a sucker of the 10th degree and deserve everything you get.
In California you are taxed even if you author software at your home. The screenwriting industry is exempted from that tax (it was targeted to get money from those who made say a million dollars working at home).