Could these people just form an LLC to get around this? So you'd be acting as a business not an individual.
I've had one for years, it costs less than $250 annual to actually maintain the LLC.
As in Schedule C, on a standard tax form? Most online tax software can handle basic LLC income.
Taxes only get complicated when you want to optimize the amount you owe. Depreciating assets, hiring, firing, claiming losses, etc.
But for many things, it's just easier for everybody to just not deal with California.