I'm currently going through the DM course. As soon as I get a couple more bonus checks I'll be getting the IDC crewpack which includes a copy of" LAW and THE DIVING PROFESSIONAL". So at this point having not read it I cannot say if one would be liable or not. But to me it would seem that if you are not working and with another group it would be hard to be assumed as being liable. It would be like a ski instructor from vermont being sued because someone on the next slope in wyoming broke his leg because he did not know how to stop. Although in the US if people who are too lazy to get up off their butts and take the stairs or keep their jowls closed can sue mickey dee's because they are fat I'm sure someone can find a shyster to sue a DM on vacation who is with a different group.