I have not looked at this project for a while and it works fine anytime I use it (mainly for my laser engraver).
There may be some future upgrades but that can be done when required.
The only thing I have noticed is that with the laser there is a distinct spot with fast movements that is very likely associated with the speed ramp down and ramp up between each movement command.
This ramp down and ramp up limits movement changes to an acceleration of less than 1 g and gives the steppers a distinctive low pitch grumble.
There are other ways of dealing with this but it is a simple system, works well and not worth upgrading.
I added a couple of useful files if your looking for motion control code:
- ArcDouble (not used for Not Grbl) but draws two arcs .
- 3DStepper does the 3d stepper motion magic.