The DOS family tree lacks FreeDOS, the last remaining maintained DOS implementation.

DOSBox. Though technically an emulator. Most people that want an easy way to run old DOS apps are probably better served with DOSBox anyway.

The DOSBox development team really likes to take their time, and often rejects outside contributions. They are only interested in running games, so will even reject bug fixes, unless you can show the bug harms some game. They are still on SourceForge and Subversion, which also acts to discourage outside contributors. Overall a rather conservative and risk-averse approach.

The forks are at GitHub, and have GitHub Actions for CI, and more modern build processes/etc. DOSBox-X wants to support running all applications, including non-games; DOSBox Staging has more of a games-centric focus, but still is much more open to new and improved features than the original DOSBox is. Both have a much faster development and release cycle, and are much more welcoming to new contributors.

DOS itself may not be a moving target, but there is still a long way to go in supporting corner cases, features of the platform which applications rarely use, etc.

[0] https://dosbox-x.com/ https://github.com/joncampbell123/dosbox-x

[1] https://dosbox-staging.github.io/ https://github.com/dosbox-staging/dosbox-staging