Is it permissible for me to accept a job offer from a competing company, knowing that my current contract requires one month's prior notice to terminate the contract, and would the owner of the other company be sinful for making this offer?

The lease is a binding contract for both parties, and neither of them is permitted to terminate it before the agreed-upon term ends, except with the consent of the other party. This is based on the Almighty's saying: "And fulfill the covenant of Allah when you have made a covenant," and the Prophet's (peace be upon him) saying: "Four characteristics, whoever possesses them is a pure hypocrite, and whoever possesses one of them possesses a characteristic of hypocrisy until he abandons it: when he speaks, he lies; when he makes a covenant, he betrays; when he promises, he breaks it; and when he disputes, he acts immorally." Therefore, if the contract between you and the first company has expired, or if it is a dissolvable contract that allows either party to terminate it at will, then there is no harm in you accepting the offer from the other company.