There have been several threads over the years regarding how to generate true open path or single line fonts for use with plotters, cnc machines etc, as well as the related font formats. I do not have the expertise to solve this problem myself, but I do want to provide the info I have collected on .OPF format fonts which are currently used with 3 consumer level desktop cnc design/driver programs. It appears that OPFs are simply intentionally broken TTF/OTF fonts given the new extension. I am providing this information in hopes that someone who shares this need can possibly take advantage of it to kick this can a little further down the road.
software that can use .opf fonts:
Make the Cut
sources for .opf fonts:
links and videos referencing
http://forum.make-the-cut.com/discussion/29705/what-exactly-is-an-opf (andy is the developer)
https://vimeo.com/45414631 (1:16:43 focus 1:32) covers how to create opf fonts