Someone in a Discord group said they all run when he tested them with his computer completely offline. He also said he will test the games in another machine tomorrow to confirm.

And most games from Amazon Prime seem to be like that, launcher-free once downloaded. Worth keeping the games somewhere safe and that Amazon's launcher can't detect, tho, as they could still get retroactively locked behind DRM in a future update.

Had hoped for more GOG offerings. Origin just doesn't make me want to download. Oh well...

Thanks. I'll download a couple of games and see if they work on a system without the Amazon launcher installed.

EDIT
I installed Fahrenheit and In Other Water and it seems you can run the games directly from the EXE without having the launcher running. Also, you can copy the whole installation folder and run it either from another folder (even after having uninstalled the launcher) or from another computer where the app was never installed.

http://www.gog.com/forum/general/amazon_prime_games_and_drm

April titles are up:
- The Elder Scrolls IV: Oblivion – Game of the Year Edition Deluxe (GOG)
- Plants vs Zombies: Battle for Neighborville (Origin)
- House of 1000 Doors: Family Secrets (Legacy Games)
- Galaxy of Pen and Paper (Amazon Games)
- Nanotale – Typing Chronicles (Amazon Games)
- Monkey Island 2 Special Edition: LeChuck’s Revenge (Amazon Games)
- Guild of Ascension (Amazon Games)
- Turnip Boy Commits Tax Evasion (Amazon Games)

The Legacy Games website (where you're supposed to redeem House of 1000 Doors) is currently having issues, but once it works you can also get a casual game for free by signing up.
https://legacygames.com/legacy-games-bonus-game/

Ends in 17 to 31 days

Neverwinter Nights: Enhanced Edition [GOG app]
SteamWorld Dig 2
Prey [GOG app]
Revita
Autonauts
Baldur's Gate II: Enhanced Edition
Roguebook
Once Upon a Jester
Gems of Destiny: Homeless Dwarf [Legacy app]

Ends in 151 days

SNK 40th Anniversary Collection
The Last Blade 2
Robo Army
Metal Slug 4
Metal Slug 3
Ninja Commando
Sengoku
Crossed Swords
Art of Fighting 3: The Path of The Warrior
Real Bout Fatal Fury 2: The Newcomers
Magician Lord
Ninja Master's
Metal Slug X
Twinkle Star Sprites
Metal Slug
The Last Blade
The King of Fighters 2003
Ghost Pilots
Super Sidekicks
Samurai Shodown IV: Amakusa's Revenge
Last Resort
3 Count Bout
Alpha Mission II
King of the Monsters 2
Kizuna Encounter: Super Tag Battle
Sengoku 2
Mutation Nation
Soccer Brawl
Over Top
The Super Spy
Top Hunter: Roddy & Cathy