The opposite of life is not “death.” The opposite is “lack of life.” There is no physical proof that death holds no life at all, and in legal terms, life ends when a victim is brain-dead, not when the body actually dies. There's a lot of trivial gray area in this.

Life and death are conceptual realities, but not necessarily absolutes.

If life exists on other planets, other realms of dimensional existence, even certain interstellar nebulae, stars, random pulses of energy -- and there is no real reason to assume they do or do not -- do they ever die? Do they know of death? ...And if not, is this enough to say that another life-form even knows of the existence of life itself?

You have difficult topics against which to argue, johannes, but then there are no true absolutes for any philosophy ... so far. Perhaps there will come a time in which we would know better ... or even worse...