A quick look at the OMIOCNC web site confirms that all of their current
products use a USB motion controller that works only with Mach3.
It should be possible to convert one of these to Mach4 by using a
board like this:
http://www.pmdx.com/PMDX-412Many low cost vendors sell machines that run only Mach3 because
they can ship it with the DEMO version of Mach3 which will cut up
to 500 lines of G-code without a license. Some even go so far as
to provide a bootleg cracked version of Mach3 along with a custom
installer which may also install malware as a bonus.
Mach4 has more stringent security requirements and the DEMO will
run for a short period of time instead of a fixed number of lines. This
makes it difficult to pretend to offer a "FREE" copy.