Strictly speaking, it mit might be against the terms of service. But if it "just" changes card texts to another language, I don't think it will be a problem, there are other tolerated extensions for the game.
The big question is always:
Do you, and the game's owner, trust the extension not to do nefarious things?
And I guess the potential damage to you (if the extension phishes your online banking passwords) is bigger than the potential damage to the game (you can't cheat by pretending to play a King's Court if you don't have one in hand, because the server knows what cards you have in hand).
The big question is always:
Do you, and the game's owner, trust the extension not to do nefarious things?
And I guess the potential damage to you (if the extension phishes your online banking passwords) is bigger than the potential damage to the game (you can't cheat by pretending to play a King's Court if you don't have one in hand, because the server knows what cards you have in hand).