If your OpenEVSE is plug in all you need is the permit for the NEMA 14-50 outlet. I would check with your city and check the permitting cost for a NEMA 14-50 "RV outlet".
Some cites charge a lot higher permitting fees for EV vs RV even though the outlet, wiring and breaker requirements are exactly the same.
I am planning to install my OpenEVSE myself, I checked with the city if I needed to get a permit or not. To which I was told it was necessary. when asking for requirements for what I needed to get the permit I was sent a copy of NEC 625 EV.
I am looking to see how much detail I need to get with the plans,