I think inactive players should be fair game no matter what but you may wanna wait for the official word from Atomic Dog. You might think about sending him a message in game as well.
Hmm I would just stay away from it, generally there are always better targets out there. If it was some random alliance I woud say ok, but we are protecting this one.
While they may be inactive, we still have an obligation to GTC. Please refrain from attacking them for now. It could be they've gone inactive but will return soon.