Apparently its no coincidence people report their play experience of 5E D&D being very reminiscent of the 1981 B/X experience. According to a series of recent posts on lead designer Mike Mearl's Facebook page, the new edition saw its genesis in Moldvay's succinct (and my favorite) iteration of the game.
According to Mearls, "The Basic D&D mods answered the question in 2012 for me - what would I add to a very simple D&D ruleset to make myself happy?"
He goes on to give us a look at what his additions were, many of which will look familiar to those who participated in the earliest playtest versions of the new edition, "Here are the house rules I applied to the 1981 Basic D&D rules. Ran game, modded to get what I wanted."
He shares those initial rules with us here:
1981 House Rules
Ability Mods: We use the 3e/4e convention (+1 or -1 per 2 above/below 10)
Saving Throws: These are ability checks, DC determined by DM
Attacks: Ability check, plus a class based bonus
Fighter: +1 every odd level
Cleric/Thief: +1 at level 3, 6, 9, 12, 15, 18
Magic-User: No bonus
Thief Abilities: These work a bit differently.
Open Locks, Find or Remove Traps, Pick Pockets, Hide in Shadows are all things only thieves can do. Hide in shadows is literally that - hide in situations where other people can’t. The thief makes a check with a bonus equal to the % listed on page B8 divided by 5.
Move Silently, Climb Sheer Surfaces, Hear Noise are all things that anyone can try. The rogue has advantage when he tries any of them.
Advantage: Roll an extra d20, take the highest result. If you get advantage more than once, take an extra die.
Disadvantage: Roll an extra die, but take the lowest. If you have advantage, disadvantage zaps one die per instance of disadvantage.
Hit Points: Upgrade everyone by one die type, you get maximum hit points at level 1 + half your Constitution score.
Hit Dice: You can use your hit dice to heal. You get hit dice equal to your total HD, spend them when resting, each die gets a bonus equal to your Con modifier.
Dwarves: Increase class’s hit die by one size. Infravision 60 feet. Can use Find or Remove Traps in underground locations.
Elves: Can alternate between magic-user and any other class, have infravision 60 feet.
Halflings: Can Hide in Shadows as a thief, get a +2 bonus to AC, but use an HD one step smaller and can’t use two-handed weapons.
Humans: Gain a +1 bonus to any two stats, or +2 to one stat (maximum 18).
Weapons: d4, d6, d8, or d12, class access based on die size
Cleric: d6, bludgeoning d8
It was funny to see the weapon damage by class house rule there at the bottom, as that's something that's been floating around the OSR for a while now (was that B/X Blackrazor's initially, I can't remember). I'll repeat my hope that some fan out there releases a home-made version of the D&D 5E Basic ruleset with all-Otus art. Good on Mearls for this insight, I can't think of a better heritage for a new edition!