In 1e, the barbarian was published in Unearthed Arcana. I don't have any data, but I've always assumed that it was a very well-known book, even if not universally liked.
El Eternauta is one of the great classics, IMO. I wonder how they will make the transposition. The author was executed, along with all of his daughters by the military regime in Argentina.
Do we really need a "scientific" explanation though?After all, it is the same universe where spaceships make whooshing sounds, fight like WW2 fighters and fall "down" along a mysterious "vertical" axis when shot...
I certainly agree that alignment is completely useless to simulate anything in real life. I also think that there are RPGs where I'm interested in some kind of simulation or real life. AD&D, for me, is not such a game.
Personally, I find the descriptive version of alignment completely useless. As a descriptor it is very weak. Alignment must have cosmological and rules oomph or I'd rather not use it.
For me, the best version by far, is AD&D 1e (yes, that includes alignment languages). 5e, IMHO, is the worst version and, for that reason, I never use alignment in 5e at all. As a descriptor I find it useless.
Unless they changed things recently, limiting something under content sharing, only precluded other participants in a campaign from reading a specific source, but all the rules options remain available for characters.