Is Using others oyster card is a crime in a bus?

Yes, using someone else's Oyster card is considered fare evasion and is illegal in the UK. It violates Transport for London's terms of use, which state that only the cardholder should use the card. If caught, you could face a penalty fare or be prosecuted, resulting in a fine or other legal consequences. Always use your own Oyster card for travel to avoid these issues.