Chex Quest (1996)
  Made by Digital Cafe for Ralston Foods. Built on the Doom engine (id Software).
  Ralston gave the game away free inside boxes of Chex cereal in 1996. It was never sold.
  General Mills bought the Chex brand in 1997 and owns it today.
  Files: chex.exe and chex.wad from the original CD (archive.org item "chex-quest-dos-files-en").
  chex.wad: 12,361,532 bytes, MD5 25485721882b050afa96a56e5758dd52.
  Hosted here unmodified, free, with no ads, for family play.

js-dos 8.5.3
  DOS emulator for the browser, based on DOSBox. Licence: GPL-2.0.
  Source: https://github.com/caiiiycuk/js-dos  (npm package "js-dos", version 8.5.3)
  Served unmodified from /js-dos/.

DOSBox
  Licence: GPL-2.0. Source: https://www.dosbox.com/