I sold a printer I manufactured and software (that I developed on top of an open source project) that runs the printer to a customer, who reached out and said their mainboard (its a motherboard in the printer with windows 10 installed and has my software and source code copied onto it) has gone bad. They are not under warranty and refused to pay for a new board from me. They then copied all of my source code and software onto another computer and are running their printer and my software off of that, to bypass buying a board from me.
Do I have any legal recourse? Is it legal for them to copy my software and source files onto another computer to run their printer?
They are also talking about making third party accessories for my printers, and altering code to enable to use of third party accessories.
I did not provide any licensing or EULA with the printer or software.