I use Cenon for my CAM. I didn’t realize it was open source and I never expected to hear anyone else mention it.
It's only the drawing portion which is:
FWIW, I tried very hard to find every possible CAD/CAM program when researching the Shapeoko wiki.... though I found Cenon because I was a long-time NeXT user.
That is why I settled on it. The other one I was working with was FabBSD. I still have the source to that it is an OpenBSD focused on CAM. I think the developer lost interest when OpenBSD switched the security model for GPIO.
I think they are both good though.
Cenon is nice, but hasn't seen much updating (but at least, being opensource gets updated as new versions are released).
Inkscape is workable, but still a bit awkward (and I doubt it will ever get all of Freehand's functionality/keyboard shortcuts).
I've been buying Serif's Affinity Designer (and their other apps), but they're still not as comfortable as FH/MX --- wish the Quasado/GraviT folks would get further along.