Assume that the person doesn't know how to correctly contribute code to an existing project. Reach out to them and gently let them know that they are welcome to contribute via Pull Requests. Also, be flattered that someone found value in your work. Assume that the other person simply doesn't know any better. If no response, or no change in a small period of time, then DMCA as mentioned in the other comment.
Assume that the person doesn't know how to correctly contribute code to an existing project. Reach out to them and gently let them know that they are welcome to contribute via Pull Requests. Also, be flattered that someone found value in your work. Assume that the other person simply doesn't know any better. If no response, or no change in a small period of time, then DMCA as mentioned in the other comment.
[0] https://en.wikipedia.org/wiki/Hanlon%27s_razor