Starcraft influenced the culture and politics of an entire nation and became a national sport. It pioneered "e-sports". It's a piece of history, and this disc is standalone a piece of history as well.
I think I know right from wrong, but I would still have absolutely no idea what to do if that disc landed on my doorstep.
Edit: I cannot believe this is such a controversial thing to say. Shame on the people who think this is an easy decision to make, put yourself in someone else's shoes for a while.
To poorly translate Victor Hugo : "The principle is twofold, let us not forget it. The book, as a book, belongs to the author, but as thought, it belongs - the word is not too vast - to the human race. All intelligences are entitled to it. If one of the two rights, the right of the writer and the right of the human mind, should be sacrificed, it would certainly be the right of the writer, for the public interest is our sole preoccupation, and All, I declare, must pass before us."
If you didn't know anything about Blizzard, what would you speculate? Someone elsewhere in the thread for example is speculating Blizzard would destroy the copy -- if I thought that'd be a possibility, I would personally never send it their way and you could in no world convince me it's moral to send a piece of history to its demise.
As for morality, I apply the golden rule: if someone found the code I wrote for a groundbreaking piece of software, and I didn't want to open source it, I'd really like for them to respect my wishes and return it.
Edit: I'm unable to reply further, but to clarify I was referring to the maxim of reciprocity or "do unto others". If the positions were reversed I'd want my property returned. If I find someone's wallet I'd return it if possible, as I'd want someone to return mine.
"The needs of the many outweigh the needs of the few" is my favorite Star Trek quote, but I don't think it applies in this situation as it was intended as a motivation for a personal decision to sacrifice, not to force someone else to sacrifice. That line of thought can get pretty dark pretty fast.
If you believe in private property rights, then sure. If not, then no. Some such as Max Stirner, 19th century philosopher, would disagree with your assertion that it is a moral issue.
Now everyone's free to be the gremlin sitting on the sack, but if that sack literally is a masterpiece that shaped the whole of civilization, one day people will gently hoist you aside and replace the sack beneath you with a sack of similar monetary value, to put your original sack in museum.
Sorry if that's inconceivable in a black and white worldview. And no - its not communism, that is civilization. A right to destroy art does not exist.
It's like I taught my children... even if you don't know whose it is, you know it isn't yours.
And in this case it is even known.
The amount of moral flexibility in these comments astounds me, although it probably shouldn't.
I would say it astounds me to find people who are as rigid as you are, but truthfully, it doesn't.