Tracktion has open-sourced the Tracktion engine:
https://www.tracktion.com/develop/tracktion-engine
Tracktion Engine is provided in JUCE module format making it incredibly quick and easy to setup and start creating projects. We’ve included a bunch of examples and accompanying tutorials along with scripts to build them so you can get up and running with the minimum of fuss. More information can be found in the repository’s README.
That’s really cool. Seems like a great starting point if anyone wants to build a new tracker 
I guess that with this and the rest of JUCE, you would have both crossplatform, vst/vst3/audio mixer/etc and HiDPI, for example.
I’m unsure how fast the JUCE software renderer is though. It seems to have quite a bit of overhead (features), so maybe even a smooth scrolling pattern in 4K would be too much?
I use Tracktion Waveform 9 on a 3K screen driven by an Intel 4700 GPU and the Juce framework seems to hold up fine, mostly.