Yep, they are probably the russian std 7.62x54 version, they are nice ! They would fetch nice sum of cash on the market.
For defensive purpose, they are still a machinegun.
Bit doubtful it would go on the market. Probably would end up in a warehouse until the conflict is over or be turned into scrap. There is a risk if they sell the gun then it may slowly get resold multiple times until it gets sold back to Ukraine.