You can sell your gadgets, widgets, themes, etc.
The ONLY Limitation is that you may not build a desktop and then export it as a GADGET (.EXE).
So for instance, we made "Natural Desktop" (www.naturaldesktop.com). We don't want someone to buy DesktopX Pro for $70 and start cranking out kiosks, desktops, etc. with it. We make a product for that called DesktopX ENTERPRISE ($500).
Gadgets should be programs, not desktops.
But other than that one limitationk, you can go nuts.
We are even setting up a site www.desktopgadgets.com to fasciliate people selling their stuff.
No, you can't distribute any desktops with pro.
A gadget is single element. If you are making something that replaces the functionality of the desktop, then it is not permitted.
examples would be: a Kiosk, a limited desktop, a theme like: https://www.wincustomize.com/Preview.aspx?Source=Chadamus/dx/3206.jpg or https://www.wincustomize.com/Preview.aspx?Source=gef/dx/3211.jpg , etc.
Actually that's the DesktopX 2 Pro license.
The DesktopX 3 Pro license is much more forgiving and can be found on the DesktopX 3 Pro purchase page:
https://www.stardock.com/products/desktopx/propurchase.asp
In summary - there is no limitation on the # of gadgets you can make nor how many people can use them. The only restriction is that you may not build a "Desktop" and then export that as a gadget. A desktop being a set of objects that are not connected together as a single unit in some way (for instance, an aquairum with fish is a desktop, the fish aren't related to one another, they're independent objects).