From my understanding, the recipe has been changed in the game for other players....just they do not see the new graphic as shown in the below image showing that they need to have grass to build a camp fire... all they are seeing is the image for the default game which is stones and logs only...not grass.....
recipes changed via the database will work fine in single player. in multiplayer they get their recipes from the local database(on their machine) this is then checked by the server when they craft it.
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When changing crafting recipes, it's a bit tricky: the actual crafting is handled serverside (so the server checks the recipe and verifies that the client has all required ingredients etc), however, the crafting UI is shown clientside (obviously). The client also checks if all ingredients are in inventory before sending a crafting request to the server (this is done to prevent the client from spamming the server with useless requests).
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