Selling Free Software <https://www.gnu.org/philosophy/selling.en.html>
> Many people believe that the spirit of the GNU Project is that you should not charge money for distributing copies of software, or that you should charge as little as possible—just enough to cover the cost. This is a misunderstanding.
> Actually, we encourage people who redistribute free software to charge as much as they wish or can. If a license does not permit users to make copies and sell them, it is a nonfree license. If this seems surprising to you, please read on.
You can buy only the firmware package as well, without the device. I'll send you the instruction on how to configure everything and which hardware modifications are required.