In the recent NEC 2017 guide I noticed there was a change requiring the 240V 14-50 outlets requiring GFCI protection now. My concern with that is how it might not like to play with the OpenEVSE units which test for ground faults at what looks like around 20mA and most GFCI like to trip at anything >6mA. Not sure if anyone has run into this yet and used the OpenEVSE charger with a 50A GFCI breaker. I am guessing, worst case I just turn off the GFCI protection in the OpenEVSE since that will be provided by the breaker.
In the UK the OpenEVSE works fine downstream of a 30mA RCD.
The rub there is, as the OP mentioned, that the GFCI (RCD) devices used in the US,
trip at 6 mA.