With the exception of UO and WW2OL, PKing in MMORPG is the player's choice. You can choose to be a PK or not be a PK. Only PKs can attack other PKs and NPKs cannot attack or be attacked.
A couple of games now allow for PK, but only under certain situations. In the case of Dark Ages of Camelot, you can only PK in the contested area between the three realms. If you stay in your realm and never venture into the contested area, you will never have to deal with PKs. In the case of EQ and AC, you have a choice and in the case of AC, you can switch between being a PK and an NPK.
Most likely, what Max is saying is they will incorperate the ability to be PK or to not be PK into the game. So, if someone doesn't want to be involved in PK, they will probably be able to very easily stay out of it.
Right now, the MMORPG I'm watching closely is the Star Wars MMORPG in the works. I'm hoping it ends up being a good game, but won't know more until it get's closer to release.