I'm not an expert when it comes to CNC machines but gcode is universal to CNC machines as far as I know. The program I use doesn't produce any machine specific code. Here is an example:

( Made using CamBam - http://www.cambam.co.uk )
( Rib Nose 9/22/2016 6:18:08 PM )
( T3 : 0.125 )
G20 G90 G91.1 G64 G40
G0 Z0.125
( T3 : 0.125 )
T3 M6
( Profile1 )
G17
M3 S1000
G0 X-0.0613 Y6.363
G0 Z0.1
G1 F10.0 Z-0.05
G3 F30.0 X-0.0274 Y6.1925 I26.433 J5.1783
This is the start of the gcode for the rib nose pieces seen in the pictures I posted above. To cut out one rib nose piece from 1/4" plywood, I move the router bit to a place on the wood piece and zero the router. When I run the code it cuts out one nose piece. I move the router and zero it again for the next piece. I believe I could use the same gcode on any CNC machine and it will cut out a same nose piece as my CNC router.

However, the gcode is based on a specific size router bit. Put in the different size router bit (or laser cut the part) with the same gcode and your part will be a different size. I've made that mistake a few times.

For sure when I outsourced the cutting, they had a program that read my drawing files and optimized the layout on my material in a few seconds. There was no extra charge for that. However, all the work was in preparing the drawing files in a format they could read. It wasn't gcode. It was AutoCAD DXF format which is a standard drawing format that plenty of programs can read. With that in mind, the DXF files are probably more useful than the gcode files.

There is no doubt that my CNC router is my favorite tool. It makes very accurate and precise parts over and over again. Would the drawing files or gcode be worthwhile to the next builder? Probably depending on how they used them. Would kit suppliers be willing to supply digital drawings or gcode? Probably not for free. Unless you have your own CNC equipment it's probably less expensive to have the kit supplier supply the parts rather than the gcode. If it's a plans built and you are sharing gcode on a user forum, that is a different story.

I don't believe there are any copyright issues. All the work I did to create the gcode is my original work.