I didn't post the link but the scanned rules and retouched cover of TSR's 1974 Barsoom Wargame is posted at the Internet Archive. At long last I have read them and they are glorious! It says Open Source but I don't know if this is an error or if it is indeed legitimately available for free. If it is not legitimate than Admin please pardon this post.
What a completely different system than I expected!
This strikes me as odd, as well - but the IA is usually thorough with the moderation; so, if it's there, maybe it's legit. Whether an item can become part of the public domain is usually regulated by the contract between the corresponding parties. So, in principle, everything is possible. Now, good luck fighting that out with the ERB estate, and Disney, to everyone who dares and does something with it.
This year I have gotten to read two games I imagined I would never lay eyes on, Milward's Heroes and now this. I have wanted to have a look at the contents of this book probably more than any other game.
Now I have hope to possibly get to read The Barsoomian Battle Manual, another Martian wargame I recently discovered after seeing it at the Facebook RPG-Auction group. Highly recommend everyone with Facebook join that group, I have behld many a rare treasure for sale there at within reason prices, including (twice now) original copies of Gods, Demigods & Heroes supplement for $25.