Language of Rusyns of Serbia. hmm I would characterize that as something between Zemplin dialect of eastern Slovak and Rusyn dialects. With some Serbian influence, of course. And they use a little more Hungarian words than modern Zemplin dialect does. Sometimes it looks more like Zemplin dialect influenced by Rusyn and Serbian but in reality it is more like Rusyn influenced by Zemplin and a bit by Serbian.
That is why it is a dialectal group sui generis, standing a bit apart from rest of Rusyn dialects and literary Rusyn.