Open Sourcing DOS 4

Original Article ↗ Hacker News Discussion ↗

Release contents and repo evolution

  • Source for MS-DOS 4.0 plus a separate tree for the early “Multitasking DOS” (MT-DOS) beta was published on GitHub.
  • Some binary/PDF folders briefly appeared under v4.0 then were moved into a v4.0-ozzie subtree for clarity.
  • There was at least one force-push to edit a personal insult in a comment (changing a full name to initials).

Historical and technical significance

  • DOS 4.0 is seen as a buggy, unpopular release; many remember 3.3/3.31 and 5.0/6.22 as the stable “peaks.”
  • The MT-DOS branch is closer to DOS 3.x with experimental multitasking and special disk drivers (bypassing BIOS on XTs, no IDE/ATA yet).
  • Comments point out 32-bit sector support in 4.0 and proprietary large-FAT variants in some OEM 3.x DOSes.
  • Several people actually built and ran MT-DOS on period IBM XT hardware, switching between apps with a hotkey.

Relation to FreeDOS, DR-DOS, and emulation

  • Many say FreeDOS and tools like DOSBox(-X), dosemu2, PCem already run “just about everything,” so this is mainly historically interesting.
  • Some retro users still prefer “period-correct” MS-DOS over FreeDOS.
  • DR-DOS/OpenDOS licensing is debated: some call it “open sourced,” others emphasize it’s only source-available with evaluation/non‑commercial restrictions.

Licensing, openness, and archival quality

  • Release uses a modern permissive license (MIT). Some argue this is unambiguous compared to DR-DOS.
  • Others criticize the “sanitization” (editing comments) and partial nature of the drop as bad archival practice, pointing to external critiques and asking for truly pristine, museum-style releases.
  • Several note legal and third‑party code issues as reasons why fuller DOS/Windows source drops are hard.

Prospects for more Microsoft source

  • Thread repeatedly asks for DOS 3.3, 5.x, 6.x, QBasic, NTVDM, Xenix, and even old Windows versions to be opened.
  • There is speculation and skepticism about ever seeing NT-based Windows or 9x source due to shared lineage with current systems and third‑party components.

Code culture, language, and nostalgia

  • People enjoy spotting in-jokes, profanity, and “brain damaged” comments, and discuss shifting norms around terms like “sanity check.”
  • Many share memories of floppies, CONFIG.SYS/AUTOEXEC.BAT tuning, TSRs, DESQview, and how early systems invited hands-on hacking in ways modern locked-down platforms often don’t.