Are they dead? This can only be answered if one has the definition of life.
Life comes in many forms and various possibilities. Humans, being sentient, are apparently alive. We also recognize animals as having life, though their sentience is in question. Plants are alive, yet are not even conscious, they simply live and reproduce. A virus defies all sense of life, except that it will reproduce, though not alone, does this count as life? If so, so too must a digital virus appear to carry life within its magnetic and electrical "DNA".
A forum does little on its own, and certainly does not produce more of its kind, yet it can be given the feel of life simply by perpetuating and allowing activity. We see this type of life other places as well; "The forest is alive". Though the forest itself is merely a location, and not an entity in its own right, we still label it with life.
What then, constitutes the end of life? A forest is dead when there is no longer any activity, a creature is dead when it no longer moves and senses, a virus is dead when it ceases to exist. A person can enter a coma for indefinite periods of time, being seemingly dead but maintaining a tiny bit of life within.
This forum still exists. This forum still senses when someone arrives, welcoming and responding without hesitation. This forum has ever so small amount of activity still clinging on to a thread. The answer then, clearly, is that this forum is not dead.