[65536]

The graphical user interface components of macOS are proprietary software, as are a bunch of other libraries included in macOS that software packaged for macOS is likely to use.

So if this was a goal of PureDarwin then they’d have a lot of work ahead of them in order to implement those APIs.

This wiki page on the repository seems to indicate that they are not intending to do that:

https://github.com/PureDarwin/PureDarwin/wiki/Graphics

> While Darwin is the operating system underlying Mac OS X, the graphical environments of PureDarwin and Mac OS X are very different. This is because most graphical aspects of Mac OS X (especially Quartz and Aqua) are proprietary, closed-source software and are not available for PureDarwin. Hence, PureDarwin uses a more traditional UNIX-like graphics system (X server), waiting a better alternative.

[zeckalpha]

https://en.m.wikipedia.org/wiki/GNUstep may help with some of this, but it is hard to keep up with a moving target.