> Isn't hobbyist effort still effort? Human labour, being duplicated? This is a feature of many FOSS projects, sadly, and I don't really get what aspect of human nature drives it, but it must be something.

Curiosity, Joy, learning, status, …

The other examples you give are all software that people use "in the real world" as a means to solve problems. The value comes from using them. The developers may also enjoy working on them, but that's mostly incidental.

I can't speak for the kolibrios contributors, but I imagine that to them, the value comes from the development process itself. They do it because they enjoy it. Any practical usefulness of the resulting software is mostly incidental.

If your goal was to develop useful software in 2023, you wouldn't be writing pure x86 assembly within the constraints of a floppy disk.

Hobbyist effort is human labor for the hobbyist's benefit, not someone else's benefit.

If the Kolibri OS folks experience unique enjoyment from developing this project that they would not obtain from Menuet OS, then the labor would not be duplicated.

- Mplayer/MPV. Mplayer works better on older machines, while MPV does work better in the newer ones.

- FVWM from TWM. Much faster and smaller.

- RXVT vs XTerm.

- Slashem from Nethack. You want Discworld references, > Nethack 3.4.3. Fullfilling role, mons and object additions, Slashem.

By this logic, playing videogames is a wasted effort, too.

"Why all these people playing Prince of Persia fight on their own? Why don't they all get together and free the Princesse once and for all?" :-)

The reason why Kolibri forked is precisely because MenuetOS stopped being F/OSS when they made the transition to 64-bit while simultaneously advertising the 64-bit version as "the future" and 32-bit as legacy.