What was White's last move? The version you have doesn't have the updated rules yet, so the black joker can't move. In the updated version, the black joker will have the ability of white's last move, which could make it a checkmate if it attacks the white king. Otherwise, it is still a stalemate under the new rules. Any piece white moves would lead to white's king being in check by the black joker. Even white moving joker (imitating a king) would make black's joker imitate a king and therefore it is still check. Since white cannot move, it's a stalemate.
Ok, diagram updated with Chancellor.
What was White's last move? The version you have doesn't have the updated rules yet, so the black joker can't move. In the updated version, the black joker will have the ability of white's last move, which could make it a checkmate if it attacks the white king. Otherwise, it is still a stalemate under the new rules. Any piece white moves would lead to white's king being in check by the black joker. Even white moving joker (imitating a king) would make black's joker imitate a king and therefore it is still check. Since white cannot move, it's a stalemate.