The world needs a new source of energy, an unspillable source.

Do I need a license to install Hydrogen fuel injection system on other people’s cars?

I live in California and was planning on getting a business license, but I was wondering if I needed a special license to put after market parts on someone else’s car.
No water goes in the system, only gas. I don’t need anyone’s opinions of whether or not it works.
I mean no water goes in the engine.