To get up and running more quickly, I'm using the linuxcncrsh interface to Machinekit.  

Linuxcncrsh is ancient compared the the current remote interface, but it's already plumbed up in openpnp, mostly.

Problem is I could never get it to initialize.  Everything went through and responds, but when I would get to sending commands the machine would be in ESTOP.

Today I figured that out.  It's a bug in linuxcncrsh itself.

SET ESTOP OFF
SET ESTOP OFF
GET ESTOP
ESTOP ON

SET ESTOP ON
SET ESTOP ON
GET ESTOP
ESTOP OFF

 Huh?  

Whatever you request for the estop state gets inverted.   

So setting estop off actually turns it on.

I can't really blame them.  I really shouldn't be using this, and it says right in the docs that it is unmaintained.

So I'm now just sending the opposite of what I want, and it seems to work.  Machine homes in openpnp too.  Now for the rest.