Hi edhamtech,
There are a lot of PCB capture programs out there and, unfortunately, no powerful open source tool that everyone uses. For sophisticated designs like Netduino Plus 2, we tend to use nice tools which help drive an excellent design--and then share all of the source for those designs for free (which can be opened with the free viewer, exported by PCB houses in a variety of formats, etc.)
I wish that Eagle was a more-premium design tool and had a free license. Or Kicad or any of the others. Maybe someday.
Our engineers have taken up Eagle for a lot of our simpler Netduino designs (GoBus modules in particular) but we're just not comfortable quality-, process- or cost-wise going that route for the more sophisticated designs.
Chris