I have a similar problem with this particular gadget.
I have noticed that the file extension is quite different from all the other gadget files. The Box_Creator_Gadget.vgadget note the extension (.vgadget) it is not install.exe like many of the other gadget files.
I also find that I am unable to get the Box Creator Gadget installed into my VCarve Pro too. I even tried changing the file extension to no avail.
The Box Creator Gadget sure looks like it would be a beneficial (time saving tool) gadget to have.
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V-Carve Pro 9.517