Open relationship basically means this: I don't wanna be tied up with you yet... I wanna go around and play...which is, for me, the very negative of reason when someone is in a relationship. RE: It's fucked up. ;-)
I guess you can find parallels with the "open system" concept in thermodynamics :-)
it's a euphemism for a relationship wherein one, or both, cheats.
I guess we all agree that the system is retarded. ;)