Un-serialized ghost guns are not legal in California. As of July 1, 2018, anyone who manufactures their own firearm must apply to the California Department of Justice for a unique serial number, or some other form of identifying mark. This is due to California’s AB857.
In addition, the law prohibits the sale or transfer of ownership of manufactured firearms. If you produce a ghost gun, whether by the Ghost Gunner or other means, it is yours, and you cannot give or sell it to anyone else.
All firearms that one manufactures and gets serialized by the California DOJ must be compliant with California state laws regarding firearms. This means no 30 round magazines or other illegal attachments/modifications.