I think the purpose is as much to create a discussion of [Free]DOS and its uses as it is to let everyone know about FreeDOS's anniversary. Besides, there may be people who aren't aware of this particular OS.

Many things on HN aren't newsworthy or are used by hardly anyone. The number of people using DOS is surely comparable to the number of people using Arc or Clojure or Erlang. Low numbers do not mean unimportance.

I take it you haven't tried to write a DOS clone?

Sometime in the early-mid 90s when Linux was still new, a bunch of "us" DOS weenies caught wind of it and tried to recreate DOS as open source. The FreeDOS book (the tiny one with a key on the cover) was passed around between us Turbo C weenies like Lion's commentary! It was a better book than "DOS Internals", the purple AW book.

I guess we can find some use cases that qualify as important. But who cares about the rounded number?